diff --git a/changelogs/unreleased/55838-remove-gem-install-bundler-from-docker-based-ruby-environments.yml b/changelogs/unreleased/55838-remove-gem-install-bundler-from-docker-based-ruby-environments.yml
new file mode 100644
index 00000000000..08f60d205df
--- /dev/null
+++ b/changelogs/unreleased/55838-remove-gem-install-bundler-from-docker-based-ruby-environments.yml
@@ -0,0 +1,5 @@
+---
+title: Remove gem install bundler from Docker-based Ruby environments
+merge_request: 24093
+author: Takuya Noguchi
+type: other
diff --git a/doc/api/lint.md b/doc/api/lint.md
index bd5a216a99d..c37a8bff749 100644
--- a/doc/api/lint.md
+++ b/doc/api/lint.md
@@ -13,7 +13,7 @@ POST /lint
 | `content`  | string    | yes      | the .gitlab-ci.yaml content|
 
 ```bash
-curl --header "Content-Type: application/json" https://gitlab.example.com/api/v4/ci/lint --data '{"content": "{ \"image\": \"ruby:2.1\", \"services\": [\"postgres\"], \"before_script\": [\"gem install bundler\", \"bundle install\", \"bundle exec rake db:create\"], \"variables\": {\"DB_NAME\": \"postgres\"}, \"types\": [\"test\", \"deploy\", \"notify\"], \"rspec\": { \"script\": \"rake spec\", \"tags\": [\"ruby\", \"postgres\"], \"only\": [\"branches\"]}}"}'
+curl --header "Content-Type: application/json" https://gitlab.example.com/api/v4/ci/lint --data '{"content": "{ \"image\": \"ruby:2.6\", \"services\": [\"postgres\"], \"before_script\": [\"bundle install\", \"bundle exec rake db:create\"], \"variables\": {\"DB_NAME\": \"postgres\"}, \"types\": [\"test\", \"deploy\", \"notify\"], \"rspec\": { \"script\": \"rake spec\", \"tags\": [\"ruby\", \"postgres\"], \"only\": [\"branches\"]}}"}'
 ```
 
 Be sure to copy paste the exact contents of `.gitlab-ci.yml` as YAML is very picky about indentation and spaces.
diff --git a/doc/api/templates/gitlab_ci_ymls.md b/doc/api/templates/gitlab_ci_ymls.md
index 8481323994b..11ec7360e06 100644
--- a/doc/api/templates/gitlab_ci_ymls.md
+++ b/doc/api/templates/gitlab_ci_ymls.md
@@ -120,6 +120,6 @@ Example response:
 ```json
 {
   "name": "Ruby",
-  "content": "# This file is a template, and might need editing before it works on your project.\n# Official language image. Look for the different tagged releases at:\n# https://hub.docker.com/r/library/ruby/tags/\nimage: \"ruby:2.3\"\n\n# Pick zero or more services to be used on all builds.\n# Only needed when using a docker container to run your tests in.\n# Check out: http://docs.gitlab.com/ce/ci/docker/using_docker_images.html#what-is-service\nservices:\n  - mysql:latest\n  - redis:latest\n  - postgres:latest\n\nvariables:\n  POSTGRES_DB: database_name\n\n# Cache gems in between builds\ncache:\n  paths:\n    - vendor/ruby\n\n# This is a basic example for a gem or script which doesn't use\n# services such as redis or postgres\nbefore_script:\n  - ruby -v                                   # Print out ruby version for debugging\n  # Uncomment next line if your rails app needs a JS runtime:\n  # - apt-get update -q && apt-get install nodejs -yqq\n  - gem install bundler  --no-document    # Bundler is not installed with the image\n  - bundle install -j $(nproc) --path vendor  # Install dependencies into ./vendor/ruby\n\n# Optional - Delete if not using `rubocop`\nrubocop:\n  script:\n  - rubocop\n\nrspec:\n  script:\n  - rspec spec\n\nrails:\n  variables:\n    DATABASE_URL: \"postgresql://postgres:postgres@postgres:5432/$POSTGRES_DB\"\n  script:\n  - bundle exec rake db:migrate\n  - bundle exec rake db:seed\n  - bundle exec rake test\n"
+  "content": "# This file is a template, and might need editing before it works on your project.\n# Official language image. Look for the different tagged releases at:\n# https://hub.docker.com/r/library/ruby/tags/\nimage: \"ruby:2.5\"\n\n# Pick zero or more services to be used on all builds.\n# Only needed when using a docker container to run your tests in.\n# Check out: http://docs.gitlab.com/ce/ci/docker/using_docker_images.html#what-is-a-service\nservices:\n  - mysql:latest\n  - redis:latest\n  - postgres:latest\n\nvariables:\n  POSTGRES_DB: database_name\n\n# Cache gems in between builds\ncache:\n  paths:\n    - vendor/ruby\n\n# This is a basic example for a gem or script which doesn't use\n# services such as redis or postgres\nbefore_script:\n  - ruby -v                                   # Print out ruby version for debugging\n  # Uncomment next line if your rails app needs a JS runtime:\n  # - apt-get update -q && apt-get install nodejs -yqq\n  - bundle install -j $(nproc) --path vendor  # Install dependencies into ./vendor/ruby\n\n# Optional - Delete if not using `rubocop`\nrubocop:\n  script:\n  - rubocop\n\nrspec:\n  script:\n  - rspec spec\n\nrails:\n  variables:\n    DATABASE_URL: \"postgresql://postgres:postgres@postgres:5432/$POSTGRES_DB\"\n  script:\n  - rails db:migrate\n  - rails db:seed\n  - rails test\n\n# This deploy job uses a simple deploy flow to Heroku, other providers, e.g. AWS Elastic Beanstalk\n# are supported too: https://github.com/travis-ci/dpl\ndeploy:\n  type: deploy\n  environment: production\n  script:\n  - gem install dpl\n  - dpl --provider=heroku --app=$HEROKU_APP_NAME --api-key=$HEROKU_PRODUCTION_KEY\n"
 }
 ```
diff --git a/doc/ci/caching/index.md b/doc/ci/caching/index.md
index 4626ccfe93d..495ec099111 100644
--- a/doc/ci/caching/index.md
+++ b/doc/ci/caching/index.md
@@ -300,7 +300,6 @@ cache:
 
 before_script:
   - ruby -v                                   # Print out ruby version for debugging
-  - gem install bundler  --no-document        # Bundler is not installed with the image
   - bundle install -j $(nproc) --path vendor  # Install dependencies into ./vendor/ruby
 
 rspec:
diff --git a/lib/gitlab/ci/templates/Ruby.gitlab-ci.yml b/lib/gitlab/ci/templates/Ruby.gitlab-ci.yml
index 51d6628c63b..0d12cbc6460 100644
--- a/lib/gitlab/ci/templates/Ruby.gitlab-ci.yml
+++ b/lib/gitlab/ci/templates/Ruby.gitlab-ci.yml
@@ -24,7 +24,6 @@ before_script:
   - ruby -v                                   # Print out ruby version for debugging
   # Uncomment next line if your rails app needs a JS runtime:
   # - apt-get update -q && apt-get install nodejs -yqq
-  - gem install bundler  --no-document        # Bundler is not installed with the image
   - bundle install -j $(nproc) --path vendor  # Install dependencies into ./vendor/ruby
 
 # Optional - Delete if not using `rubocop`
diff --git a/spec/controllers/projects/ci/lints_controller_spec.rb b/spec/controllers/projects/ci/lints_controller_spec.rb
index 82c1374aa4f..cfa010c2d1c 100644
--- a/spec/controllers/projects/ci/lints_controller_spec.rb
+++ b/spec/controllers/projects/ci/lints_controller_spec.rb
@@ -51,7 +51,6 @@ describe Projects::Ci::LintsController do
         - apt-get update -qq && apt-get install -y -qq sqlite3 libsqlite3-dev nodejs
         - ruby -v
         - which ruby
-        - gem install bundler --no-ri --no-rdoc
         - bundle install --jobs $(nproc)  "${FLAGS[@]}"
       HEREDOC
     end
diff --git a/spec/fixtures/gitlab/ci/external_files/.gitlab-ci-template-1.yml b/spec/fixtures/gitlab/ci/external_files/.gitlab-ci-template-1.yml
index 0bab94a7c2e..1e88cd120aa 100644
--- a/spec/fixtures/gitlab/ci/external_files/.gitlab-ci-template-1.yml
+++ b/spec/fixtures/gitlab/ci/external_files/.gitlab-ci-template-1.yml
@@ -2,7 +2,6 @@ before_script:
   - apt-get update -qq && apt-get install -y -qq sqlite3 libsqlite3-dev nodejs
   - ruby -v
   - which ruby
-  - gem install bundler --no-ri --no-rdoc
   - bundle install --jobs $(nproc)  "${FLAGS[@]}"
 
 rspec:
diff --git a/spec/lib/gitlab/ci/config/external/file/local_spec.rb b/spec/lib/gitlab/ci/config/external/file/local_spec.rb
index 541deb13b97..645db642e29 100644
--- a/spec/lib/gitlab/ci/config/external/file/local_spec.rb
+++ b/spec/lib/gitlab/ci/config/external/file/local_spec.rb
@@ -44,7 +44,6 @@ describe Gitlab::Ci::Config::External::File::Local do
             - apt-get update -qq && apt-get install -y -qq sqlite3 libsqlite3-dev nodejs
             - ruby -v
             - which ruby
-            - gem install bundler --no-ri --no-rdoc
             - bundle install --jobs $(nproc)  "${FLAGS[@]}"
         HEREDOC
       end
diff --git a/spec/lib/gitlab/ci/config/external/file/remote_spec.rb b/spec/lib/gitlab/ci/config/external/file/remote_spec.rb
index 7c1a1c38736..eaf621e4140 100644
--- a/spec/lib/gitlab/ci/config/external/file/remote_spec.rb
+++ b/spec/lib/gitlab/ci/config/external/file/remote_spec.rb
@@ -11,7 +11,6 @@ describe Gitlab::Ci::Config::External::File::Remote do
         - apt-get update -qq && apt-get install -y -qq sqlite3 libsqlite3-dev nodejs
         - ruby -v
         - which ruby
-        - gem install bundler --no-ri --no-rdoc
         - bundle install --jobs $(nproc)  "${FLAGS[@]}"
     HEREDOC
   end
diff --git a/spec/lib/gitlab/ci/config/external/processor_spec.rb b/spec/lib/gitlab/ci/config/external/processor_spec.rb
index 1a05f716247..dbd28e9745c 100644
--- a/spec/lib/gitlab/ci/config/external/processor_spec.rb
+++ b/spec/lib/gitlab/ci/config/external/processor_spec.rb
@@ -51,7 +51,6 @@ describe Gitlab::Ci::Config::External::Processor do
           - apt-get update -qq && apt-get install -y -qq sqlite3 libsqlite3-dev nodejs
           - ruby -v
           - which ruby
-          - gem install bundler --no-ri --no-rdoc
           - bundle install --jobs $(nproc)  "${FLAGS[@]}"
 
         rspec:
@@ -86,7 +85,6 @@ describe Gitlab::Ci::Config::External::Processor do
           - apt-get update -qq && apt-get install -y -qq sqlite3 libsqlite3-dev nodejs
           - ruby -v
           - which ruby
-          - gem install bundler --no-ri --no-rdoc
           - bundle install --jobs $(nproc)  "${FLAGS[@]}"
         HEREDOC
       end
diff --git a/spec/lib/gitlab/ci/config_spec.rb b/spec/lib/gitlab/ci/config_spec.rb
index 975e11e8cc1..ea6f1e20014 100644
--- a/spec/lib/gitlab/ci/config_spec.rb
+++ b/spec/lib/gitlab/ci/config_spec.rb
@@ -170,7 +170,6 @@ describe Gitlab::Ci::Config do
         before_script_values = [
           "apt-get update -qq && apt-get install -y -qq sqlite3 libsqlite3-dev nodejs", "ruby -v",
           "which ruby",
-          "gem install bundler --no-ri --no-rdoc",
           "bundle install --jobs $(nproc)  \"${FLAGS[@]}\""
         ]
         variables = {
diff --git a/spec/support/gitlab_stubs/gitlab_ci.yml b/spec/support/gitlab_stubs/gitlab_ci.yml
index e55a61b2b94..f3755e52b2c 100644
--- a/spec/support/gitlab_stubs/gitlab_ci.yml
+++ b/spec/support/gitlab_stubs/gitlab_ci.yml
@@ -1,9 +1,8 @@
-image: ruby:2.1
+image: ruby:2.6
 services:
   - postgres
 
 before_script:
-  - gem install bundler
   - bundle install
   - bundle exec rake db:create