diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 028a2d2..cdbde68 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -24,3 +24,10 @@ jobs:
       - run: bundle install --jobs=3 --retry=3 --path=vendor/bundle
       - run: bundle exec rake spec
         continue-on-error: ${{ matrix.entry.allowed-failure }}
+      - name: Specs for when the i18n gem is not available
+        run: |
+          cd spec_i18n
+          bundle install --jobs=3 --retry=3
+          pwd
+          bundle exec rake spec
+        continue-on-error: ${{ matrix.entry.allowed-failure }}
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ec2fbe2..eae4f4a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ### 1.0.0 (Next)
 
+* [#41](https://github.com/dblock/ruby-enum/pull/41): Make i18n dependency optional - [@peterfication](https://github.com/peterfication).
 * [#43](https://github.com/dblock/ruby-enum/pull/43): Add exhaustive case matcher - [@peterfication](https://github.com/peterfication).
 * [#40](https://github.com/dblock/ruby-enum/pull/39): Enable new Rubocop cops and address/allowlist lints - [@petergoldstein](https://github.com/petergoldstein).
 * [#39](https://github.com/dblock/ruby-enum/pull/39): Require Ruby >= 2.7 - [@petergoldstein](https://github.com/petergoldstein).
diff --git a/README.md b/README.md
index 5e6ba08..49ab445 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,7 @@ Enum-like behavior for Ruby, heavily inspired by [this](http://www.rubyfleebie.c
   - [Duplicate enumerator keys or duplicate values](#duplicate-enumerator-keys-or-duplicate-values)
   - [Inheritance](#inheritance)
   - [Exhaustive case matcher](#exhaustive-case-matcher)
+  - [I18n support](#i18n-support)
 - [Benchmarks](#benchmarks)
 - [Contributing](#contributing)
 - [Copyright and License](#copyright-and-license)
@@ -300,6 +301,15 @@ Color.Case(color, {
 })
 ```
 
+### I18n support
+
+This gem has an optional dependency to `i18n`. If it's available, the error messages will have a nice description and can be translated. If it's not available, the errors will only contain the message keys.
+
+```ruby
+# Add this to your Gemfile if you want to have a nice error description instead of just a message key.
+gem "i18n"
+```
+
 ## Benchmarks
 
 Benchmark scripts are defined in the [`benchmarks`](benchmarks) folder and can be run with Rake:
diff --git a/lib/ruby-enum.rb b/lib/ruby-enum.rb
index 0404a0a..4d9b921 100644
--- a/lib/ruby-enum.rb
+++ b/lib/ruby-enum.rb
@@ -1,12 +1,23 @@
 # frozen_string_literal: true
 
-require 'i18n'
-
 require 'ruby-enum/version'
 require 'ruby-enum/enum'
 require 'ruby-enum/enum/case'
+require 'ruby-enum/enum/i18n_mock'
+
+# Try to load the I18n gem and provide a mock if it is not available.
+begin
+  require 'i18n'
+  Ruby::Enum.i18n = I18n
+rescue LoadError
+  # I18n is not available
+  # :nocov:
+  # Tests for this loading are in the spec_i18n folder
+  Ruby::Enum.i18n = Ruby::Enum::I18nMock
+  # :nocov:
+end
 
-I18n.load_path << File.join(File.dirname(__FILE__), 'config', 'locales', 'en.yml')
+Ruby::Enum.i18n.load_path << File.join(File.dirname(__FILE__), 'config', 'locales', 'en.yml')
 
 require 'ruby-enum/errors/base'
 require 'ruby-enum/errors/uninitialized_constant_error'
diff --git a/lib/ruby-enum/enum.rb b/lib/ruby-enum/enum.rb
index 2c94626..0930e86 100644
--- a/lib/ruby-enum/enum.rb
+++ b/lib/ruby-enum/enum.rb
@@ -2,6 +2,11 @@
 
 module Ruby
   module Enum
+    class << self
+      # Needed for I18n mock
+      attr_accessor :i18n
+    end
+
     attr_reader :key, :value
 
     def initialize(key, value)
diff --git a/lib/ruby-enum/enum/i18n_mock.rb b/lib/ruby-enum/enum/i18n_mock.rb
new file mode 100644
index 0000000..b9adbb9
--- /dev/null
+++ b/lib/ruby-enum/enum/i18n_mock.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+# :nocov:
+module Ruby
+  module Enum
+    ##
+    # Mock I18n module in case the i18n gem is not available.
+    module I18nMock
+      def self.load_path
+        []
+      end
+
+      def self.translate(key, _options = {})
+        key
+      end
+    end
+  end
+end
+# :nocov:
diff --git a/lib/ruby-enum/errors/base.rb b/lib/ruby-enum/errors/base.rb
index 66cc604..5ab2ee1 100644
--- a/lib/ruby-enum/errors/base.rb
+++ b/lib/ruby-enum/errors/base.rb
@@ -39,7 +39,7 @@ def compose_message(key, attributes = {})
         #
         # Returns a localized error message string.
         def translate(key, options)
-          ::I18n.translate("#{BASE_KEY}.#{key}", locale: :en, **options).strip
+          Ruby::Enum.i18n.translate("#{BASE_KEY}.#{key}", locale: :en, **options).strip
         end
 
         # Create the problem.
diff --git a/ruby-enum.gemspec b/ruby-enum.gemspec
index 46fe6e0..50da6a9 100644
--- a/ruby-enum.gemspec
+++ b/ruby-enum.gemspec
@@ -16,6 +16,5 @@ Gem::Specification.new do |s|
   s.homepage = 'http://github.com/dblock/ruby-enum'
   s.licenses = ['MIT']
   s.summary = 'Enum-like behavior for Ruby.'
-  s.add_dependency 'i18n'
   s.metadata['rubygems_mfa_required'] = 'true'
 end
diff --git a/spec/ruby-enum/enum_spec.rb b/spec/ruby-enum/enum_spec.rb
index 3cb3b30..bd0f1c9 100644
--- a/spec/ruby-enum/enum_spec.rb
+++ b/spec/ruby-enum/enum_spec.rb
@@ -23,8 +23,24 @@ class SecondSubclass < FirstSubclass
     expect(Colors::GREEN).to eq 'green'
   end
 
-  it 'raises UninitializedConstantError on an invalid constant' do
-    expect { Colors::ANYTHING }.to raise_error Ruby::Enum::Errors::UninitializedConstantError, /The constant Colors::ANYTHING has not been defined./
+  context 'when the i18n gem is loaded' do
+    it 'raises UninitializedConstantError on an invalid constant' do
+      expect do
+        Colors::ANYTHING
+      end.to raise_error Ruby::Enum::Errors::UninitializedConstantError, /The constant Colors::ANYTHING has not been defined./
+    end
+  end
+
+  context 'when the i18n gem is not loaded' do
+    before do
+      allow(described_class).to receive(:i18n).and_return(Ruby::Enum::I18nMock)
+    end
+
+    it 'raises UninitializedConstantError on an invalid constant' do
+      expect do
+        Colors::ANYTHING
+      end.to raise_error Ruby::Enum::Errors::UninitializedConstantError, /ruby.enum.errors.messages.uninitialized_constant.summary/
+    end
   end
 
   describe '#each' do
@@ -151,22 +167,54 @@ class SecondSubclass < FirstSubclass
   end
 
   context 'when a duplicate key is used' do
-    it 'raises DuplicateKeyError' do
-      expect do
-        Colors.class_eval do
-          define :RED, 'some'
-        end
-      end.to raise_error Ruby::Enum::Errors::DuplicateKeyError, /The constant Colors::RED has already been defined./
+    context 'when the i18n gem is loaded' do
+      it 'raises DuplicateKeyError' do
+        expect do
+          Colors.class_eval do
+            define :RED, 'some'
+          end
+        end.to raise_error Ruby::Enum::Errors::DuplicateKeyError, /The constant Colors::RED has already been defined./
+      end
+    end
+
+    context 'when the i18n gem is not loaded' do
+      before do
+        allow(described_class).to receive(:i18n).and_return(Ruby::Enum::I18nMock)
+      end
+
+      it 'raises DuplicateKeyError' do
+        expect do
+          Colors.class_eval do
+            define :RED, 'some'
+          end
+        end.to raise_error Ruby::Enum::Errors::DuplicateKeyError, /ruby.enum.errors.messages.duplicate_key.message/
+      end
     end
   end
 
   context 'when a duplicate value is used' do
-    it 'raises a DuplicateValueError' do
-      expect do
-        Colors.class_eval do
-          define :Other, 'red'
-        end
-      end.to raise_error Ruby::Enum::Errors::DuplicateValueError, /The value red has already been defined./
+    context 'when the i18n gem is loaded' do
+      it 'raises a DuplicateValueError' do
+        expect do
+          Colors.class_eval do
+            define :Other, 'red'
+          end
+        end.to raise_error Ruby::Enum::Errors::DuplicateValueError, /The value red has already been defined./
+      end
+    end
+
+    context 'when the i18n gem is not loaded' do
+      before do
+        allow(described_class).to receive(:i18n).and_return(Ruby::Enum::I18nMock)
+      end
+
+      it 'raises a DuplicateValueError' do
+        expect do
+          Colors.class_eval do
+            define :Other, 'red'
+          end
+        end.to raise_error Ruby::Enum::Errors::DuplicateValueError, /ruby.enum.errors.messages.duplicate_value.summary/
+      end
     end
   end
 
diff --git a/spec_i18n/Gemfile b/spec_i18n/Gemfile
new file mode 100644
index 0000000..84d9f8e
--- /dev/null
+++ b/spec_i18n/Gemfile
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+source 'http://rubygems.org'
+
+gemspec path: '../', name: 'ruby-enum'
+
+# This Gemfile should not include any gem that has i18n as a dependency.
+gem 'rake'
+gem 'rspec', '~> 3.0'
diff --git a/spec_i18n/Rakefile b/spec_i18n/Rakefile
new file mode 100644
index 0000000..9827cdf
--- /dev/null
+++ b/spec_i18n/Rakefile
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+require 'rubygems'
+
+require 'rspec/core'
+require 'rspec/core/rake_task'
+
+RSpec::Core::RakeTask.new(:spec) do |spec|
+  spec.pattern = FileList['spec/**/*_spec.rb']
+end
+
+task default: %i[spec]
diff --git a/spec_i18n/spec/i18n_spec.rb b/spec_i18n/spec/i18n_spec.rb
new file mode 100644
index 0000000..082ca05
--- /dev/null
+++ b/spec_i18n/spec/i18n_spec.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+test_class = Class.new do
+  include Ruby::Enum
+
+  define :RED, 'red'
+  define :GREEN, 'green'
+end
+
+describe Ruby::Enum do
+  context 'when the i18n gem is not loaded' do
+    it 'raises UninitializedConstantError on an invalid constant' do
+      expect do
+        test_class::ANYTHING
+      end.to raise_error Ruby::Enum::Errors::UninitializedConstantError, /ruby.enum.errors.messages.uninitialized_constant.summary/
+    end
+  end
+
+  context 'when a duplicate key is used' do
+    context 'when the i18n gem is not loaded' do
+      before do
+        allow(described_class).to receive(:i18n).and_return(Ruby::Enum::I18nMock)
+      end
+
+      it 'raises DuplicateKeyError' do
+        expect do
+          test_class.class_eval do
+            define :RED, 'some'
+          end
+        end.to raise_error Ruby::Enum::Errors::DuplicateKeyError, /ruby.enum.errors.messages.duplicate_key.message/
+      end
+    end
+  end
+
+  context 'when a duplicate value is used' do
+    context 'when the i18n gem is not loaded' do
+      before do
+        allow(described_class).to receive(:i18n).and_return(Ruby::Enum::I18nMock)
+      end
+
+      it 'raises a DuplicateValueError' do
+        expect do
+          test_class.class_eval do
+            define :Other, 'red'
+          end
+        end.to raise_error Ruby::Enum::Errors::DuplicateValueError, /ruby.enum.errors.messages.duplicate_value.summary/
+      end
+    end
+  end
+end
diff --git a/spec_i18n/spec/spec_helper.rb b/spec_i18n/spec/spec_helper.rb
new file mode 100644
index 0000000..cf56090
--- /dev/null
+++ b/spec_i18n/spec/spec_helper.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+$LOAD_PATH.unshift(File.join(File.dirname(__FILE__), '..', '..', 'lib'))
+
+require 'rubygems'
+
+require 'rspec'
+require 'ruby-enum'