diff --git a/Gemfile b/Gemfile
index be5ae2e8cd9..a7f7e19b01d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -45,6 +45,7 @@ gem 'net-smtp', require: false # TODO: Remove it if you use rails 7.0.1
 gem 'newspaper'
 gem 'oauth2'
 gem 'omniauth', '~> 2.1.1'
+gem 'omniauth-discord'
 gem 'omniauth-github', '~> 2.0.1'
 gem 'omniauth-rails_csrf_protection'
 gem 'parser', '3.2.2.4'
diff --git a/Gemfile.lock b/Gemfile.lock
index badcafdd4c7..eb34d223cf6 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -329,6 +329,8 @@ GEM
       hashie (>= 3.4.6)
       rack (>= 2.2.3)
       rack-protection
+    omniauth-discord (1.2.0)
+      omniauth-oauth2 (~> 1.6)
     omniauth-github (2.0.1)
       omniauth (~> 2.0)
       omniauth-oauth2 (~> 1.8)
@@ -638,6 +640,7 @@ DEPENDENCIES
   newspaper
   oauth2
   omniauth (~> 2.1.1)
+  omniauth-discord
   omniauth-github (~> 2.0.1)
   omniauth-rails_csrf_protection
   parser (= 3.2.2.4)
diff --git a/app/controllers/user_sessions_controller.rb b/app/controllers/user_sessions_controller.rb
index 3b408ccc193..adec92fc69b 100644
--- a/app/controllers/user_sessions_controller.rb
+++ b/app/controllers/user_sessions_controller.rb
@@ -35,32 +35,32 @@ def destroy
     redirect_to root_url, notice: 'ログアウトしました。'
   end
 
-  # rubocop:disable Metrics/MethodLength
   def callback
     auth = request.env['omniauth.auth']
-    github_id = auth[:uid]
-    if current_user.blank?
-      user = User.find_by(github_id:)
-      if user.blank?
-        flash[:alert] = 'ログインに失敗しました。先にアカウントを作成後、GitHub連携を行ってください。'
-        redirect_to root_url
-      elsif user.retired_on?
-        logout
-        redirect_to retire_path
-      else
-        session[:user_id] = user.id
-        redirect_back_or_to root_url, notice: 'サインインしました。'
+    authentication =
+      case params[:provider]
+      when 'discord'
+        Authentication::Discord.new(current_user, auth)
+      when 'github'
+        Authentication::Github.new(current_user, auth)
       end
-    else
-      github_account = auth[:info][:nickname]
-      current_user.register_github_account(github_id, github_account) if current_user.github_id.blank?
-      flash[:notice] = 'GitHubと連携しました。'
-      redirect_to root_path
-    end
-  rescue StandardError => e
-    logger.warn "[GitHub Login] ログインに失敗しました。：#{e.message}"
-    flash[:alert] = 'GitHubログインに失敗しました。数回試しても続く場合、管理者に連絡してください。'
-    redirect_to root_path
+    result = authentication.authenticate
+    assign_flash_and_session(result)
+
+    return redirect_back_or_to result[:path] if result[:back]
+
+    redirect_to result[:path]
+  end
+
+  def failure
+    redirect_to root_path, alert: 'キャンセルしました'
+  end
+
+  private
+
+  def assign_flash_and_session(result)
+    flash[:notice] = result[:notice] if result[:notice]
+    flash[:alert] = result[:alert] if result[:alert]
+    session[:user_id] = result[:user_id] if result[:user_id]
   end
-  # rubocop:enable Metrics/MethodLength
 end
diff --git a/app/models/authentication/discord.rb b/app/models/authentication/discord.rb
new file mode 100644
index 00000000000..6e7f9aa1bd0
--- /dev/null
+++ b/app/models/authentication/discord.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+class Authentication::Discord
+  include Rails.application.routes.url_helpers
+
+  def initialize(login_user, auth)
+    @login_user = login_user
+    @auth = auth
+  end
+
+  def authenticate
+    if link
+      { path: root_path, notice: 'Discordと連携しました' }
+    else
+      { path: root_path, alert: 'Discordの連携に失敗しました' }
+    end
+  end
+
+  private
+
+  def link
+    discord_profile = DiscordProfile.find_or_initialize_by(user: @login_user)
+    discord_profile.account_name = @auth[:info][:name]
+    discord_profile.save
+  end
+end
diff --git a/app/models/authentication/github.rb b/app/models/authentication/github.rb
new file mode 100644
index 00000000000..1ac94028132
--- /dev/null
+++ b/app/models/authentication/github.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+class Authentication::Github
+  include Rails.application.routes.url_helpers
+
+  def initialize(user, auth)
+    @user = user
+    @auth = auth
+  end
+
+  def authenticate
+    if @user.blank?
+      user = User.find_by(github_id: @auth[:uid])
+      if user.blank?
+        { path: root_path, alert: 'ログインに失敗しました。先にアカウントを作成後、GitHub連携を行ってください。' }
+      elsif user.retired_on?
+        { path: retirement_path }
+      else
+        { path: root_path, notice: 'サインインしました。', user_id: user.id, back: true }
+      end
+    else
+      link if @user.github_id.blank?
+      { path: root_path, notice: 'GitHubと連携しました。' }
+    end
+  rescue StandardError => e
+    Rails.logger.warn "[GitHub Login] ログインに失敗しました。：#{e.message}"
+    { path: root_path, alert: 'GitHubログインに失敗しました。数回試しても続く場合、管理者に連絡してください。' }
+  end
+
+  private
+
+  def link
+    @user.github_account = @auth[:info][:nickname]
+    @user.github_id = @auth[:uid]
+    @user.save!
+  end
+end
diff --git a/app/models/user.rb b/app/models/user.rb
index 2d0ca9efb79..ff87a5900da 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -619,12 +619,6 @@ def participating?(event)
     send(method_name).include?(event)
   end
 
-  def register_github_account(id, account_name)
-    self.github_account = account_name
-    self.github_id = id
-    save!
-  end
-
   def depressed?
     reported_reports = reports.order(reported_on: :desc).limit(DEPRESSED_SIZE)
     reported_reports.size == DEPRESSED_SIZE && reported_reports.all?(&:sad?)
diff --git a/app/views/users/form/_company.html.slim b/app/views/users/form/_company.html.slim
index 5db2edeff9d..51321ea92b2 100644
--- a/app/views/users/form/_company.html.slim
+++ b/app/views/users/form/_company.html.slim
@@ -4,18 +4,15 @@
     = f.collection_select :company_id, desc_ordered_companies_with_empty, :id, :name, {}, { id: 'js-choices-single-select' }
   .a-form-help
     - if user.admin?
-      p フィヨルドを選択。
+      p 株式会社ロッカを選択。
     - elsif user.mentor?
       p
-        | もし良かったら所属企業を登録してください。
-        | 所属企業がない場合は管理者にご連絡をお願いします。
+        | 差し支えがなければ所属企業（どこかの企業に所属している場合は）を登録してください。
     - elsif user.adviser?
       p
         | 所属企業を登録してください。研修でお使いいただいている場合は、
         | 所属企業を登録することで研修生の日報、提出物の通知が飛ぶようになります。
     - elsif user.graduated_on?
       p
-        | もし良かったら所属企業を登録してください。
+        | 差し支えがなければ所属企業を登録してください。
         | 所属企業の登録は必須ではありません。
-        | 所属企業がない場合は管理者にご連絡をお願いします。
-    end
diff --git a/app/views/users/form/_sns.html.slim b/app/views/users/form/_sns.html.slim
index 62767add59d..361843398ab 100644
--- a/app/views/users/form/_sns.html.slim
+++ b/app/views/users/form/_sns.html.slim
@@ -2,18 +2,20 @@
   .form-item
     label.a-form-label
       | Discord アカウント
-    .form-item__mention-input
-      = discord_profile_fields.text_field :account_name, class: 'a-text-input', placeholder: 'komagata1111'
-    .a-form-help
-      p
-        | Discord で使用しているアカウント名を入力してください。
-      p
-        | Discord のアカウントの調べ方は
-        label.a-form-help-link.is-danger(for='modal-discord-account')
-          span.a-form-help-link__label
-            | こちら
-          span.a-help
-            i.fa-solid.fa-question
+    - if f.object.discord_profile.account_name?
+      .form-item__mention-input
+        = discord_profile_fields.text_field :account_name, class: 'a-text-input', disabled: true
+      .a-form-help
+        p Discord アカウントは登録されています。
+    - else
+      = link_to '/auth/discord', class: 'a-button is-sm is-primary', method: :post do
+        p Discord アカウントを登録する
+      .a-form-help
+        p
+          | 今後、Discord とフィヨルドブートキャンプアプリとの
+          | 連携に Discord アカウントの登録が必要になります。
+          | フィヨルドブートキャンプの Discord サーバに入室をしたら、
+          | 必ず登録をしてください。
 
   .form-item#times-url
     = discord_profile_fields.label :times_url, class: 'a-form-label'
diff --git a/config/initializers/omniauth.rb b/config/initializers/omniauth.rb
index c0a86baa777..43d9e8ace16 100644
--- a/config/initializers/omniauth.rb
+++ b/config/initializers/omniauth.rb
@@ -2,4 +2,7 @@
 
 Rails.application.config.middleware.use OmniAuth::Builder do
   provider :github, ENV["GITHUB_KEY"], ENV["GITHUB_SECRET"], scope: 'user:email'
+  provider :discord, ENV['DISCORD_CLIENT_ID'], ENV['DISCORD_CLIENT_SECRET']
+
+  OmniAuth.config.on_failure = proc { |_env| [302, {'Location' => '/auth/failure', 'Content-Type'=> 'text/html'}, []] }
 end
diff --git a/config/routes.rb b/config/routes.rb
index 92decbf390f..948ee5396d5 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -91,7 +91,8 @@
   get "pages/tags/:tag", to: "pages#index", as: :pages_tag, tag: /.+/, format: "html"
   get "questions/tags/:tag", to: "questions#index", as: :questions_tag, tag: /.+/, format: "html"
   get "login" => "user_sessions#new", as: :login
-  get "auth/github/callback" => "user_sessions#callback"
+  get "auth/:provider/callback" => "user_sessions#callback"
+  get 'auth/failure', to: "user_sessions#failure"
   post "user_sessions" => "user_sessions#create"
   get "logout" => "user_sessions#destroy", as: :logout
   get "thanks", to: "static_pages#thanks"
diff --git a/test/models/authentication/discord_test.rb b/test/models/authentication/discord_test.rb
new file mode 100644
index 00000000000..933cb4bd37f
--- /dev/null
+++ b/test/models/authentication/discord_test.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class Authentication::DiscordTest < ActiveSupport::TestCase
+  include Rails.application.routes.url_helpers
+
+  test 'authentication succeeds when arguments are valid' do
+    user = users(:komagata)
+    discord_authentication = Authentication::Discord.new(user, { info: { name: 'komagata_discord' } })
+    result = discord_authentication.authenticate
+
+    assert_equal result[:notice], 'Discordと連携しました'
+    assert_equal result[:path], root_path
+  end
+
+  test 'authentication fails when arguments are invalid' do
+    discord_authentication = Authentication::Discord.new(nil, { info: { name: 'komagata_discord' } })
+    result = discord_authentication.authenticate
+
+    assert_equal result[:alert], 'Discordの連携に失敗しました'
+    assert_equal result[:path], root_path
+  end
+end
diff --git a/test/models/authentication/github_test.rb b/test/models/authentication/github_test.rb
new file mode 100644
index 00000000000..15a4ce119d6
--- /dev/null
+++ b/test/models/authentication/github_test.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class Authentication::GithubTest < ActiveSupport::TestCase
+  include Rails.application.routes.url_helpers
+
+  test 'authentication fails when github id does not match' do
+    github_authentication = Authentication::Github.new(nil, { info: { nickname: 'kimura_github' }, uid: 'uid_test_data' })
+    result = github_authentication.authenticate
+
+    assert_equal result[:path], root_path
+    assert_equal result[:alert], 'ログインに失敗しました。先にアカウントを作成後、GitHub連携を行ってください。'
+  end
+
+  test 'retirement path when github id matches a retired user' do
+    user = users(:yameo)
+    user.github_id = 'uid_test_data'
+    user.save!
+
+    github_authentication = Authentication::Github.new(nil, { info: { nickname: 'yameo_github' }, uid: 'uid_test_data' })
+
+    assert_equal github_authentication.authenticate[:path], retirement_path
+  end
+
+  test 'authentication succeeds when github id matches a regular user' do
+    user = users(:kimura)
+    user.github_id = 'uid_test_data'
+    user.save!
+
+    github_authentication = Authentication::Github.new(nil, { info: { name: 'komagata_discord' }, uid: 'uid_test_data' })
+    result = github_authentication.authenticate
+
+    assert_equal result[:path], root_path
+    assert_equal result[:notice], 'サインインしました。'
+    assert_equal result[:user_id], user.id
+    assert_equal result[:back], true
+  end
+
+  test 'github is linked when user is logged in and not linked with Github' do
+    user = users(:kimura)
+    github_authentication = Authentication::Github.new(user, { info: { nickname: 'kimura_github' }, uid: 'uid_test_data' })
+    result = github_authentication.authenticate
+
+    assert_equal result[:path], root_path
+    assert_equal user.reload.github_account, 'kimura_github'
+    assert_equal user.reload.github_id, 'uid_test_data'
+  end
+end
diff --git a/test/system/authentication/discord_test.rb b/test/system/authentication/discord_test.rb
new file mode 100644
index 00000000000..8b1fde53cff
--- /dev/null
+++ b/test/system/authentication/discord_test.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require 'application_system_test_case'
+
+class Authentication::DiscordSystemTest < ApplicationSystemTestCase
+  setup do
+    OmniAuth.config.test_mode = true
+    OmniAuth.config.add_mock(:discord, { info: { name: 'discord_name' } })
+  end
+
+  test 'cannot register discord account already setting user' do
+    visit_with_auth '/current_user/edit', 'kimura'
+
+    assert_text 'Discord アカウントは登録されています。'
+    assert_no_text 'Discord アカウントを登録する'
+  end
+
+  test 'can register discord account not setting user' do
+    visit_with_auth '/current_user/edit', 'hatsuno'
+
+    click_link 'Discord アカウントを登録する'
+    assert_text 'Discordと連携しました'
+
+    visit '/current_user/edit'
+    assert_text 'Discord アカウントは登録されています。'
+  end
+end
diff --git a/test/system/sign_in_with_github_test.rb b/test/system/authentication/github_test.rb
similarity index 93%
rename from test/system/sign_in_with_github_test.rb
rename to test/system/authentication/github_test.rb
index d45950cba50..80961d05a2b 100644
--- a/test/system/sign_in_with_github_test.rb
+++ b/test/system/authentication/github_test.rb
@@ -2,7 +2,7 @@
 
 require 'application_system_test_case'
 
-class SignInWithGithubTest < ApplicationSystemTestCase
+class Authentication::GithubSystemTest < ApplicationSystemTestCase
   fixtures :users
 
   setup do