diff --git a/Project.toml b/Project.toml
index ff99b0ec9..2270c1ae2 100644
--- a/Project.toml
+++ b/Project.toml
@@ -7,6 +7,7 @@ Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"
 FillArrays = "1a297f60-69ca-5386-bcde-b61e274b549b"
 LineSearches = "d3d80556-e9d4-5f37-9878-2ab0fcc64255"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+MathOptInterface = "b8f27783-ece8-5eb3-8dc8-9495eed66fee"
 NLSolversBase = "d41bc354-129a-5804-8e4c-c37616107c6c"
 NaNMath = "77ba4419-2d1f-58cd-9bb1-8ffee604a2e3"
 Parameters = "d96e819e-fc66-5662-9728-84c9c7592b0a"
@@ -19,6 +20,7 @@ StatsBase = "2913bbd2-ae8a-5f71-8c99-4fb6c76f3a91"
 Compat = "3.2.0, 3.3.0, 3.4.0, 3.5.0, 3.6.0"
 FillArrays = "0.6.2, 0.7, 0.8, 0.9, 0.10, 0.11"
 LineSearches = "7.0.1"
+MathOptInterface = "0.9.22"
 NLSolversBase = "7.8.0"
 NaNMath = "0.3.2"
 Parameters = "0.10, 0.11, 0.12"
diff --git a/src/MOI_wrapper.jl b/src/MOI_wrapper.jl
new file mode 100644
index 000000000..04e22f218
--- /dev/null
+++ b/src/MOI_wrapper.jl
@@ -0,0 +1,444 @@
+import MathOptInterface
+const MOI = MathOptInterface
+const MOIU = MathOptInterface.Utilities
+
+mutable struct VariableInfo{T}
+    lower_bound::T  # May be -Inf even if has_lower_bound == true
+    has_lower_bound::Bool # Implies lower_bound == Inf
+    upper_bound::T  # May be Inf even if has_upper_bound == true
+    has_upper_bound::Bool # Implies upper_bound == Inf
+    is_fixed::Bool        # Implies lower_bound == upper_bound and !has_lower_bound and !has_upper_bound.
+    start::Union{Nothing,T}
+end
+
+VariableInfo{T}() where {T} = VariableInfo(typemin(T), false, typemax(T), false, false, nothing)
+
+function starting_value(v::VariableInfo{T}) where {T}
+    if v.start !== nothing
+        return v.start
+    else
+        if v.has_lower_bound && v.has_upper_bound
+            if zero(T) <= v.lower_bound
+                return v.lower_bound
+            elseif v.upper_bound <= zero(T)
+                return v.upper_bound
+            else
+                return zero(T)
+            end
+        elseif v.has_lower_bound
+            return max(zero(T), v.lower_bound)
+        else
+            return min(zero(T), v.upper_bound)
+        end
+    end
+end
+
+const LE{T} = MOI.LessThan{T}
+const GE{T} = MOI.GreaterThan{T}
+const EQ{T} = MOI.EqualTo{T}
+
+mutable struct Optimizer{T} <: MOI.AbstractOptimizer
+    # Problem data.
+    variable_info::Vector{VariableInfo{T}}
+    nlp_data::Union{MOI.NLPBlockData,Nothing}
+    sense::MOI.OptimizationSense
+
+    # Parameters.
+    method::Union{AbstractOptimizer,Nothing}
+    silent::Bool
+    options::Dict{Symbol,Any}
+
+    # Solution attributes.
+    results::Union{Nothing,MultivariateOptimizationResults}
+end
+
+function Optimizer{T}() where {T}
+    return Optimizer{T}(
+        VariableInfo{T}[],
+        nothing,
+        MOI.FEASIBILITY_SENSE,
+        nothing,
+        false,
+        Dict{Symbol,Any}(),
+        nothing,
+    )
+end
+Optimizer() = Optimizer{Float64}()
+
+MOI.supports(::Optimizer, ::MOI.NLPBlock) = true
+
+MOI.supports(::Optimizer, ::MOI.ObjectiveSense) = true
+MOI.supports(::Optimizer, ::MOI.Silent) = true
+function MOI.supports(::Optimizer, p::MOI.RawParameter)
+    return p.name == "method" || hasfield(Options, Symbol(p.name))
+end
+
+function MOI.supports(::Optimizer, ::MOI.VariablePrimalStart, ::Type{MOI.VariableIndex})
+    return true
+end
+
+MOI.supports_constraint(::Optimizer{T}, ::Type{MOI.SingleVariable}, ::Type{LE{T}}) where {T} = true
+MOI.supports_constraint(::Optimizer{T}, ::Type{MOI.SingleVariable}, ::Type{GE{T}}) where {T} = true
+MOI.supports_constraint(::Optimizer{T}, ::Type{MOI.SingleVariable}, ::Type{EQ{T}}) where {T} = true
+
+MOIU.supports_default_copy_to(::Optimizer, copy_names::Bool) = !copy_names
+
+function MOI.copy_to(model::Optimizer, src::MOI.ModelLike; copy_names = false)
+    return MOIU.default_copy_to(model, src, copy_names)
+end
+
+MOI.get(::Optimizer, ::MOI.SolverName) = "Optim"
+
+function MOI.set(model::Optimizer, ::MOI.ObjectiveSense, sense::MOI.OptimizationSense)
+    model.sense = sense
+    return
+end
+
+function MOI.set(model::Optimizer, ::MOI.Silent, value::Bool)
+    model.silent = value
+    return
+end
+
+MOI.get(model::Optimizer, ::MOI.Silent) = model.silent
+
+const TIME_LIMIT = "time_limit"
+MOI.supports(::Optimizer, ::MOI.TimeLimitSec) = true
+function MOI.set(model::Optimizer, ::MOI.TimeLimitSec, value::Real)
+    MOI.set(model, MOI.RawParameter(TIME_LIMIT), Float64(value))
+end
+function MOI.set(model::Optimizer, attr::MOI.TimeLimitSec, ::Nothing)
+    delete!(model.options, TIME_LIMIT)
+end
+function MOI.get(model::Optimizer, ::MOI.TimeLimitSec)
+    return get(model.options, TIME_LIMIT, nothing)
+end
+
+function MOI.set(model::Optimizer, p::MOI.RawParameter, value)
+    model.options[p.name] = value
+    return
+end
+
+function MOI.get(model::Optimizer, p::MOI.RawParameter)
+    if haskey(model.options, p.name)
+        return model.options[p.name]
+    end
+    error("RawParameter with name $(p.name) is not set.")
+end
+
+MOI.get(model::Optimizer, ::MOI.SolveTime) = model.solve_time
+
+function MOI.empty!(model::Optimizer)
+    empty!(model.variable_info)
+    model.nlp_data = nothing
+    model.sense = MOI.FEASIBILITY_SENSE
+    model.results = nothing
+    return
+end
+
+function MOI.is_empty(model::Optimizer)
+    return isempty(model.variable_info) &&
+           model.nlp_data === nothing &&
+           model.sense == MOI.FEASIBILITY_SENSE
+end
+
+function MOI.add_variable(model::Optimizer{T}) where {T}
+    push!(model.variable_info, VariableInfo{T}())
+    return MOI.VariableIndex(length(model.variable_info))
+end
+function MOI.is_valid(model::Optimizer, vi::MOI.VariableIndex)
+    return vi.value in eachindex(model.variable_info)
+end
+function MOI.is_valid(model::Optimizer{T}, ci::MOI.ConstraintIndex{MOI.SingleVariable,LE{T}}) where {T}
+    vi = MOI.VariableIndex(ci.value)
+    return MOI.is_valid(model, vi) && has_upper_bound(model, vi)
+end
+function MOI.is_valid(model::Optimizer{T}, ci::MOI.ConstraintIndex{MOI.SingleVariable,GE{T}}) where {T}
+    vi = MOI.VariableIndex(ci.value)
+    return MOI.is_valid(model, vi) && has_lower_bound(model, vi)
+end
+function MOI.is_valid(model::Optimizer{T}, ci::MOI.ConstraintIndex{MOI.SingleVariable,EQ{T}}) where {T}
+    vi = MOI.VariableIndex(ci.value)
+    return MOI.is_valid(model, vi) && is_fixed(model, vi)
+end
+
+function has_upper_bound(model::Optimizer, vi::MOI.VariableIndex)
+    return model.variable_info[vi.value].has_upper_bound
+end
+
+function has_lower_bound(model::Optimizer, vi::MOI.VariableIndex)
+    return model.variable_info[vi.value].has_lower_bound
+end
+
+function is_fixed(model::Optimizer, vi::MOI.VariableIndex)
+    return model.variable_info[vi.value].is_fixed
+end
+
+function MOI.add_constraint(model::Optimizer{T}, v::MOI.SingleVariable, lt::LE{T}) where {T}
+    vi = v.variable
+    MOI.throw_if_not_valid(model, vi)
+    if isnan(lt.upper)
+        error("Invalid upper bound value $(lt.upper).")
+    end
+    if has_upper_bound(model, vi)
+        throw(MOI.UpperBoundAlreadySet{typeof(lt),typeof(lt)}(vi))
+    end
+    if is_fixed(model, vi)
+        throw(MOI.UpperBoundAlreadySet{EQ{T},typeof(lt)}(vi))
+    end
+    model.variable_info[vi.value].upper_bound = lt.upper
+    model.variable_info[vi.value].has_upper_bound = true
+    return MOI.ConstraintIndex{MOI.SingleVariable,LE{T}}(vi.value)
+end
+
+function MOI.add_constraint(model::Optimizer{T}, v::MOI.SingleVariable, gt::MOI.GreaterThan{T}) where {T}
+    vi = v.variable
+    MOI.throw_if_not_valid(model, vi)
+    if isnan(gt.lower)
+        error("Invalid lower bound value $(gt.lower).")
+    end
+    if has_lower_bound(model, vi)
+        throw(MOI.LowerBoundAlreadySet{typeof(gt),typeof(gt)}(vi))
+    end
+    if is_fixed(model, vi)
+        throw(MOI.LowerBoundAlreadySet{EQ{T},typeof(gt)}(vi))
+    end
+    model.variable_info[vi.value].lower_bound = gt.lower
+    model.variable_info[vi.value].has_lower_bound = true
+    return MOI.ConstraintIndex{MOI.SingleVariable,GE{T}}(vi.value)
+end
+
+function MOI.add_constraint(model::Optimizer{T}, v::MOI.SingleVariable, eq::EQ{T}) where {T}
+    vi = v.variable
+    MOI.throw_if_not_valid(model, vi)
+    if isnan(eq.value)
+        error("Invalid fixed value $(gt.lower).")
+    end
+    if has_lower_bound(model, vi)
+        throw(MOI.LowerBoundAlreadySet{GE{T},typeof(eq)}(vi))
+    end
+    if has_upper_bound(model, vi)
+        throw(MOI.UpperBoundAlreadySet{LE{T},typeof(eq)}(vi))
+    end
+    if is_fixed(model, vi)
+        throw(MOI.LowerBoundAlreadySet{typeof(eq),typeof(eq)}(vi))
+    end
+    model.variable_info[vi.value].lower_bound = eq.value
+    model.variable_info[vi.value].upper_bound = eq.value
+    model.variable_info[vi.value].is_fixed = true
+    return MOI.ConstraintIndex{MOI.SingleVariable,EQ{T}}(vi.value)
+end
+
+function MOI.set(
+    model::Optimizer,
+    ::MOI.VariablePrimalStart,
+    vi::MOI.VariableIndex,
+    value::Union{Real,Nothing},
+)
+    MOI.throw_if_not_valid(model, vi)
+    model.variable_info[vi.value].start = value
+    return
+end
+
+function MOI.set(model::Optimizer, ::MOI.NLPBlock, nlp_data::MOI.NLPBlockData)
+    model.nlp_data = nlp_data
+    return
+end
+
+function requested_features(::ZerothOrderOptimizer, has_constraints)
+    return Symbol[]
+end
+function requested_features(::FirstOrderOptimizer, has_constraints)
+    features = [:Grad]
+    if has_constraints
+        push!(features, :Jac)
+    end
+    return features
+end
+function requested_features(::Union{IPNewton,SecondOrderOptimizer}, has_constraints)
+    features = [:Grad, :Hess]
+    if has_constraints
+        push!(features, :Jac)
+    end
+    return features
+end
+
+function sparse_to_dense!(A, I::Vector{Tuple{Int,Int}}, nzval)
+    for k in eachindex(I)
+        i, j = I[k]
+        A[i, j] += nzval[k]
+    end
+    return A
+end
+
+function sym_sparse_to_dense!(A, I::Vector{Tuple{Int,Int}}, nzval)
+    for k in eachindex(I)
+        i, j = I[k]
+        A[i, j] += nzval[k]
+        A[j, i] = A[i, j]
+    end
+    return A
+end
+
+function MOI.optimize!(model::Optimizer{T}) where {T}
+    num_variables = length(model.variable_info)
+
+    # load parameters
+    if model.nlp_data === nothing || !model.nlp_data.has_objective
+        error("An objective should be provided to Optim with `@NLobjective`.")
+    end
+    objective_scale = model.sense == MOI.MAX_SENSE ? -one(T) : one(T)
+    zero_μ = zeros(T, length(model.nlp_data.constraint_bounds))
+    function f(x)
+        return objective_scale * MOI.eval_objective(model.nlp_data.evaluator, x)
+    end
+    function g!(G, x)
+        fill!(G, zero(T))
+        MOI.eval_objective_gradient(model.nlp_data.evaluator, G, x)
+        if model.sense == MOI.MAX_SENSE
+            rmul!(G, objective_scale)
+        end
+        return G
+    end
+    function h!(H, x)
+        fill!(H, zero(T))
+        MOI.eval_hessian_lagrangian(model.nlp_data.evaluator, H_nzval, x, objective_scale, zero_μ)
+        sym_sparse_to_dense!(H, hessian_structure, H_nzval)
+        return H
+    end
+
+    method = model.method
+    nl_constrained = !isempty(model.nlp_data.constraint_bounds)
+    features = MOI.features_available(model.nlp_data.evaluator)
+    if method === nothing
+        if nl_constrained
+            method = IPNewton()
+        elseif :Grad in features
+            if :Hess in features
+                method = fallback_method(f, g!, h!)
+            else
+                method = fallback_method(f, g!)
+            end
+        else
+            method = fallback_method(f)
+        end
+    end
+    MOI.initialize(model.nlp_data.evaluator, requested_features(method, nl_constrained))
+
+    if :Hess in features
+        hessian_structure = MOI.hessian_lagrangian_structure(model.nlp_data.evaluator)
+        H_nzval = zeros(T, length(hessian_structure))
+    end
+
+    initial_x = starting_value.(model.variable_info)
+    options = copy(model.options)
+    has_bounds = any(info -> info.is_fixed || info.has_upper_bound || info.has_lower_bound, model.variable_info)
+    if has_bounds
+        lower = [info.lower_bound for info in model.variable_info]
+        upper = [info.upper_bound for info in model.variable_info]
+    end
+    if !nl_constrained && has_bounds && !(method isa IPNewton)
+        options = Options(; options)
+        model.results = optimize(f, g!, lower, upper, initial_x, Fminbox(method), options; inplace = true)
+    else
+        d = promote_objtype(method, initial_x, :finite, true, f, g!, h!)
+        add_default_opts!(options, method)
+        options = Options(; options...)
+        if nl_constrained || has_bounds
+            if nl_constrained
+                lc = [b.lower for b in model.nlp_data.constraint_bounds]
+                uc = [b.upper for b in model.nlp_data.constraint_bounds]
+                c!(c, x) = MOI.eval_constraint(model.nlp_data.evaluator, c, x)
+                if !(:Jac in features)
+                    error("Nonlinear constraints should be differentiable to be used with Optim.")
+                end
+                if !(:Hess in features)
+                    error("Nonlinear constraints should be twice differentiable to be used with Optim.")
+                end
+                jacobian_structure = MOI.jacobian_structure(model.nlp_data.evaluator)
+                J_nzval = zeros(T, length(jacobian_structure))
+                function jacobian!(J, x)
+                    fill!(J, zero(T))
+                    MOI.eval_constraint_jacobian(model.nlp_data.evaluator, J_nzval, x)
+                    sparse_to_dense!(J, jacobian_structure, J_nzval)
+                    return J
+                end
+                function con_hessian!(H, x, λ)
+                    fill!(H, zero(T))
+                    MOI.eval_hessian_lagrangian(model.nlp_data.evaluator, H_nzval, x, zero(T), λ)
+                    sym_sparse_to_dense!(H, hessian_structure, H_nzval)
+                    return H
+                end
+                if !has_bounds
+                    lower = fill(typemin(T), num_variables)
+                    upper = fill(typemax(T), num_variables)
+                end
+                c = TwiceDifferentiableConstraints(
+                    c!, jacobian!, con_hessian!,
+                    lower, upper, lc, uc,
+                )
+            else
+                @assert has_bounds
+                c = TwiceDifferentiableConstraints(lower, upper)
+            end
+            model.results = optimize(d, c, initial_x, method, options)
+        else
+            model.results = optimize(d, initial_x, method, options)
+        end
+    end
+    return
+end
+
+function MOI.get(model::Optimizer, ::MOI.TerminationStatus)
+    if model.results === nothing
+        return MOI.OPTIMIZE_NOT_CALLED
+    elseif converged(model.results)
+        return MOI.LOCALLY_SOLVED
+    else
+        return MOI.OTHER_ERROR
+    end
+end
+
+function MOI.get(model::Optimizer, ::MOI.RawStatusString)
+    return summary(model.results)
+end
+
+# Ipopt always has an iterate available.
+function MOI.get(model::Optimizer, ::MOI.ResultCount)
+    return model.results === nothing ? 0 : 1
+end
+
+function MOI.get(model::Optimizer, attr::MOI.PrimalStatus)
+    if !(1 <= attr.N <= MOI.get(model, MOI.ResultCount()))
+        return MOI.NO_SOLUTION
+    end
+    if converged(model.results)
+        return MOI.FEASIBLE_POINT
+    else
+        return MOI.UNKNOWN_RESULT_STATUS
+    end
+end
+
+function MOI.get(model::Optimizer, attr::MOI.ObjectiveValue)
+    MOI.check_result_index_bounds(model, attr)
+    val = minimum(model.results)
+    if model.sense == MOI.MAX_SENSE
+        val = -val
+    end
+    return val
+end
+
+function MOI.get(model::Optimizer, attr::MOI.VariablePrimal, vi::MOI.VariableIndex)
+    MOI.check_result_index_bounds(model, attr)
+    MOI.throw_if_not_valid(model, vi)
+    return minimizer(model.results)[vi.value]
+end
+
+function MOI.get(
+    model::Optimizer,
+    attr::MOI.ConstraintPrimal,
+    ci::MOI.ConstraintIndex{MOI.SingleVariable,<:Union{LE,MOI.GreaterThan{Float64},EQ}},
+)
+    MOI.check_result_index_bounds(model, attr)
+    MOI.throw_if_not_valid(model, ci)
+    return minimizer(model.results)[ci.value]
+end
diff --git a/src/Optim.jl b/src/Optim.jl
index cde1b3e10..71c415963 100644
--- a/src/Optim.jl
+++ b/src/Optim.jl
@@ -215,4 +215,7 @@ include("multivariate/solvers/constrained/ipnewton/utilities/trace.jl")
 # Maximization convenience wrapper
 include("maximize.jl")
 
+# MathOptInterface wrapper
+include("MOI_wrapper.jl")
+
 end
diff --git a/test/MOI_wrapper.jl b/test/MOI_wrapper.jl
new file mode 100644
index 000000000..dd2165f81
--- /dev/null
+++ b/test/MOI_wrapper.jl
@@ -0,0 +1,68 @@
+module TestOptim
+
+import Optim
+using MathOptInterface
+using Test
+
+const MOI = MathOptInterface
+
+const OPTIMIZER_CONSTRUCTOR = MOI.OptimizerWithAttributes(
+    Optim.Optimizer{Float64},
+    MOI.Silent() => true,
+)
+const OPTIMIZER = MOI.instantiate(OPTIMIZER_CONSTRUCTOR)
+const CACHED = MOI.Utilities.CachingOptimizer(
+    MOI.Utilities.UniversalFallback(MOI.Utilities.Model{Float64}()),
+    OPTIMIZER,
+)
+
+const CONFIG = MOI.Test.TestConfig(
+    atol = 1e-6,
+    rtol = 1e-6,
+    duals = false,
+    query = false,
+    infeas_certificates = false,
+    optimal_status = MOI.LOCALLY_SOLVED,
+)
+
+function test_SolverName()
+    @test MOI.get(OPTIMIZER, MOI.SolverName()) == "Optim"
+end
+
+function test_supports_incremental_interface()
+    @test TestOptim.MOI.Utilities.supports_default_copy_to(OPTIMIZER, false)
+    @test !TestOptim.MOI.Utilities.supports_default_copy_to(OPTIMIZER, true)
+end
+
+function test_nlp()
+    MOI.Test.nlptest(CACHED, CONFIG, String[
+        # FIXME The hessian callback for constraints is called with
+        # `λ = [-Inf, 0.0]` and then we get `NaN`, ...
+        "hs071",
+        # There are nonlinear constraints so we need `IPNewton` but `IPNewton` needs a hessian.
+        "hs071_no_hessian", "feasibility_sense_with_objective_and_no_hessian",
+        # FIXME Here there is no hessian but there is a hessian-vector product, can `IPNewton` work with that ?
+        "hs071_hessian_vector_product_test",
+        # No objective, would be fixed by https://github.com/jump-dev/MathOptInterface.jl/issues/1397
+        "feasibility_sense_with_no_objective_and_with_hessian",
+        "feasibility_sense_with_no_objective_and_no_hessian",
+        # Affine objective, would be fixed by https://github.com/jump-dev/MathOptInterface.jl/issues/1397
+        "nlp_objective_and_moi_objective",
+        #"feasibility_sense_with_no_objective_and_with_hessian",
+    ])
+end
+
+# This function runs all functions in this module starting with `test_`.
+function runtests()
+    for name in names(@__MODULE__; all = true)
+        if startswith("$(name)", "test_")
+            @testset "$(name)" begin
+                getfield(@__MODULE__, name)()
+            end
+        end
+    end
+end
+
+end # module TestOptim
+
+TestOptim.runtests()
diff --git a/test/runtests.jl b/test/runtests.jl
index 7e7ffbe51..8fe8db299 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -260,3 +260,7 @@ println("Literate examples")
     o = Optim.Options()
     @test occursin(" = ", sprint(show, o))
 end
+
+@testset "MOI wrapper" begin
+    include("MOI_wrapper.jl")
+end