diff --git a/compiler/rustc_smir/src/rustc_internal/mod.rs b/compiler/rustc_smir/src/rustc_internal/mod.rs
index 441aafd1257ba..1a9dea99f643f 100644
--- a/compiler/rustc_smir/src/rustc_internal/mod.rs
+++ b/compiler/rustc_smir/src/rustc_internal/mod.rs
@@ -86,6 +86,10 @@ impl<'tcx> Tables<'tcx> {
         stable_mir::ty::ImplDef(self.create_def_id(did))
     }
 
+    pub fn region_def(&mut self, did: DefId) -> stable_mir::ty::RegionDef {
+        stable_mir::ty::RegionDef(self.create_def_id(did))
+    }
+
     pub fn prov(&mut self, aid: AllocId) -> stable_mir::ty::Prov {
         stable_mir::ty::Prov(self.create_alloc_id(aid))
     }
diff --git a/compiler/rustc_smir/src/rustc_smir/mod.rs b/compiler/rustc_smir/src/rustc_smir/mod.rs
index 5ff17613b4e56..c6c97ce35e8b9 100644
--- a/compiler/rustc_smir/src/rustc_smir/mod.rs
+++ b/compiler/rustc_smir/src/rustc_smir/mod.rs
@@ -7,7 +7,8 @@
 //!
 //! For now, we are developing everything inside `rustc`, thus, we keep this module private.
 
-use hir::def::DefKind;
+use crate::rustc_smir::hir::def::DefKind;
+use crate::rustc_smir::stable_mir::ty::{BoundRegion, EarlyBoundRegion, Region};
 use rustc_hir as hir;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::{alloc_range, AllocId};
@@ -1500,9 +1501,39 @@ impl<'tcx> Stable<'tcx> for ty::ImplPolarity {
 impl<'tcx> Stable<'tcx> for ty::Region<'tcx> {
     type T = stable_mir::ty::Region;
 
-    fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
-        // FIXME: add a real implementation of stable regions
-        opaque(self)
+    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        Region { kind: self.kind().stable(tables) }
+    }
+}
+
+impl<'tcx> Stable<'tcx> for ty::RegionKind<'tcx> {
+    type T = stable_mir::ty::RegionKind;
+
+    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        use stable_mir::ty::RegionKind;
+        match self {
+            ty::ReEarlyBound(early_reg) => RegionKind::ReEarlyBound(EarlyBoundRegion {
+                def_id: tables.region_def(early_reg.def_id),
+                index: early_reg.index,
+                name: early_reg.name.to_string(),
+            }),
+            ty::ReLateBound(db_index, bound_reg) => RegionKind::ReLateBound(
+                db_index.as_u32(),
+                BoundRegion { var: bound_reg.var.as_u32(), kind: bound_reg.kind.stable(tables) },
+            ),
+            ty::ReStatic => RegionKind::ReStatic,
+            ty::RePlaceholder(place_holder) => {
+                RegionKind::RePlaceholder(stable_mir::ty::Placeholder {
+                    universe: place_holder.universe.as_u32(),
+                    bound: BoundRegion {
+                        var: place_holder.bound.var.as_u32(),
+                        kind: place_holder.bound.kind.stable(tables),
+                    },
+                })
+            }
+            ty::ReErased => RegionKind::ReErased,
+            _ => unreachable!("{self:?}"),
+        }
     }
 }
 
diff --git a/compiler/stable_mir/src/fold.rs b/compiler/stable_mir/src/fold.rs
index 16ae62311aaf0..4e0b4bc7a73a5 100644
--- a/compiler/stable_mir/src/fold.rs
+++ b/compiler/stable_mir/src/fold.rs
@@ -4,17 +4,20 @@ use crate::Opaque;
 
 use super::ty::{
     Allocation, Binder, Const, ConstDef, ConstantKind, ExistentialPredicate, FnSig, GenericArgKind,
-    GenericArgs, Promoted, RigidTy, TermKind, Ty, TyKind, UnevaluatedConst,
+    GenericArgs, Promoted, Region, RigidTy, TermKind, Ty, TyKind, UnevaluatedConst,
 };
 
 pub trait Folder: Sized {
     type Break;
-    fn visit_ty(&mut self, ty: &Ty) -> ControlFlow<Self::Break, Ty> {
+    fn fold_ty(&mut self, ty: &Ty) -> ControlFlow<Self::Break, Ty> {
         ty.super_fold(self)
     }
     fn fold_const(&mut self, c: &Const) -> ControlFlow<Self::Break, Const> {
         c.super_fold(self)
     }
+    fn fold_reg(&mut self, reg: &Region) -> ControlFlow<Self::Break, Region> {
+        reg.super_fold(self)
+    }
 }
 
 pub trait Foldable: Sized + Clone {
@@ -26,7 +29,7 @@ pub trait Foldable: Sized + Clone {
 
 impl Foldable for Ty {
     fn fold<V: Folder>(&self, folder: &mut V) -> ControlFlow<V::Break, Self> {
-        folder.visit_ty(self)
+        folder.fold_ty(self)
     }
     fn super_fold<V: Folder>(&self, folder: &mut V) -> ControlFlow<V::Break, Self> {
         let mut kind = self.kind();
@@ -106,6 +109,15 @@ impl Foldable for GenericArgs {
     }
 }
 
+impl Foldable for Region {
+    fn fold<V: Folder>(&self, folder: &mut V) -> ControlFlow<V::Break, Self> {
+        folder.fold_reg(self)
+    }
+    fn super_fold<V: Folder>(&self, _: &mut V) -> ControlFlow<V::Break, Self> {
+        ControlFlow::Continue(self.clone())
+    }
+}
+
 impl Foldable for GenericArgKind {
     fn super_fold<V: Folder>(&self, folder: &mut V) -> ControlFlow<V::Break, Self> {
         let mut this = self.clone();
@@ -136,7 +148,10 @@ impl Foldable for RigidTy {
             }
             RigidTy::Slice(inner) => *inner = inner.fold(folder)?,
             RigidTy::RawPtr(ty, _) => *ty = ty.fold(folder)?,
-            RigidTy::Ref(_, ty, _) => *ty = ty.fold(folder)?,
+            RigidTy::Ref(reg, ty, _) => {
+                *reg = reg.fold(folder)?;
+                *ty = ty.fold(folder)?
+            }
             RigidTy::FnDef(_, args) => *args = args.fold(folder)?,
             RigidTy::FnPtr(sig) => *sig = sig.fold(folder)?,
             RigidTy::Closure(_, args) => *args = args.fold(folder)?,
@@ -214,7 +229,7 @@ pub enum Never {}
 impl Folder for GenericArgs {
     type Break = Never;
 
-    fn visit_ty(&mut self, ty: &Ty) -> ControlFlow<Self::Break, Ty> {
+    fn fold_ty(&mut self, ty: &Ty) -> ControlFlow<Self::Break, Ty> {
         ControlFlow::Continue(match ty.kind() {
             TyKind::Param(p) => self[p],
             _ => *ty,
diff --git a/compiler/stable_mir/src/ty.rs b/compiler/stable_mir/src/ty.rs
index 82007e3068340..6029e3c11adef 100644
--- a/compiler/stable_mir/src/ty.rs
+++ b/compiler/stable_mir/src/ty.rs
@@ -1,7 +1,7 @@
 use super::{
     mir::Safety,
     mir::{Body, Mutability},
-    with, AllocId, DefId,
+    with, AllocId, DefId, Symbol,
 };
 use crate::Opaque;
 use std::fmt::{self, Debug, Formatter};
@@ -34,7 +34,46 @@ pub struct Const {
 }
 
 type Ident = Opaque;
-pub type Region = Opaque;
+
+#[derive(Debug, Clone)]
+pub struct Region {
+    pub kind: RegionKind,
+}
+
+#[derive(Debug, Clone)]
+pub enum RegionKind {
+    ReEarlyBound(EarlyBoundRegion),
+    ReLateBound(DebruijnIndex, BoundRegion),
+    ReStatic,
+    RePlaceholder(Placeholder<BoundRegion>),
+    ReErased,
+}
+
+pub(crate) type DebruijnIndex = u32;
+
+#[derive(Debug, Clone)]
+pub struct EarlyBoundRegion {
+    pub def_id: RegionDef,
+    pub index: u32,
+    pub name: Symbol,
+}
+
+pub(crate) type BoundVar = u32;
+
+#[derive(Debug, Clone)]
+pub struct BoundRegion {
+    pub var: BoundVar,
+    pub kind: BoundRegionKind,
+}
+
+pub(crate) type UniverseIndex = u32;
+
+#[derive(Debug, Clone)]
+pub struct Placeholder<T> {
+    pub universe: UniverseIndex,
+    pub bound: T,
+}
+
 #[derive(Clone, Copy, PartialEq, Eq)]
 pub struct Span(pub usize);
 
@@ -152,6 +191,9 @@ pub struct ConstDef(pub DefId);
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct ImplDef(pub DefId);
 
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct RegionDef(pub DefId);
+
 #[derive(Clone, Debug)]
 pub struct GenericArgs(pub Vec<GenericArgKind>);
 
diff --git a/compiler/stable_mir/src/visitor.rs b/compiler/stable_mir/src/visitor.rs
index 9c3b4cd994a48..961009581388d 100644
--- a/compiler/stable_mir/src/visitor.rs
+++ b/compiler/stable_mir/src/visitor.rs
@@ -4,7 +4,7 @@ use crate::Opaque;
 
 use super::ty::{
     Allocation, Binder, Const, ConstDef, ExistentialPredicate, FnSig, GenericArgKind, GenericArgs,
-    Promoted, RigidTy, TermKind, Ty, UnevaluatedConst,
+    Promoted, Region, RigidTy, TermKind, Ty, UnevaluatedConst,
 };
 
 pub trait Visitor: Sized {
@@ -15,6 +15,9 @@ pub trait Visitor: Sized {
     fn visit_const(&mut self, c: &Const) -> ControlFlow<Self::Break> {
         c.super_visit(self)
     }
+    fn visit_reg(&mut self, reg: &Region) -> ControlFlow<Self::Break> {
+        reg.super_visit(self)
+    }
 }
 
 pub trait Visitable {
@@ -101,6 +104,16 @@ impl Visitable for GenericArgs {
     }
 }
 
+impl Visitable for Region {
+    fn visit<V: Visitor>(&self, visitor: &mut V) -> ControlFlow<V::Break> {
+        visitor.visit_reg(self)
+    }
+
+    fn super_visit<V: Visitor>(&self, _: &mut V) -> ControlFlow<V::Break> {
+        ControlFlow::Continue(())
+    }
+}
+
 impl Visitable for GenericArgKind {
     fn super_visit<V: Visitor>(&self, visitor: &mut V) -> ControlFlow<V::Break> {
         match self {
@@ -128,7 +141,10 @@ impl Visitable for RigidTy {
             }
             RigidTy::Slice(inner) => inner.visit(visitor),
             RigidTy::RawPtr(ty, _) => ty.visit(visitor),
-            RigidTy::Ref(_, ty, _) => ty.visit(visitor),
+            RigidTy::Ref(reg, ty, _) => {
+                reg.visit(visitor);
+                ty.visit(visitor)
+            }
             RigidTy::FnDef(_, args) => args.visit(visitor),
             RigidTy::FnPtr(sig) => sig.visit(visitor),
             RigidTy::Closure(_, args) => args.visit(visitor),