diff --git a/.env.production.sample b/.env.production.sample
index 13e89b40d2..7de5e00f40 100644
--- a/.env.production.sample
+++ b/.env.production.sample
@@ -285,3 +285,7 @@ MAX_POLL_OPTION_CHARS=100
 # Units are in bytes
 MAX_EMOJI_SIZE=51200
 MAX_REMOTE_EMOJI_SIZE=204800
+
+# Optional hCaptcha support
+# HCAPTCHA_SECRET_KEY=
+# HCAPTCHA_SITE_KEY=
diff --git a/Gemfile b/Gemfile
index eae5f11b7c..67c50d19fa 100644
--- a/Gemfile
+++ b/Gemfile
@@ -156,3 +156,5 @@ gem 'concurrent-ruby', require: false
 gem 'connection_pool', require: false
 
 gem 'xorcist', '~> 1.1'
+
+gem 'hcaptcha', '~> 7.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index 8d72732ebb..cc9a53e410 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -271,6 +271,8 @@ GEM
       railties (>= 4.0.1)
     hashdiff (1.0.1)
     hashie (4.1.0)
+    hcaptcha (7.1.0)
+      json
     highline (2.0.3)
     hiredis (0.6.3)
     hkdf (0.3.0)
@@ -719,6 +721,7 @@ DEPENDENCIES
   fog-openstack (~> 0.3)
   fuubar (~> 2.5)
   hamlit-rails (~> 0.2)
+  hcaptcha (~> 7.1)
   hiredis (~> 0.6)
   htmlentities (~> 4.3)
   http (~> 5.0)
diff --git a/app/controllers/auth/confirmations_controller.rb b/app/controllers/auth/confirmations_controller.rb
index 0b5a2f3c9d..17ad56fa87 100644
--- a/app/controllers/auth/confirmations_controller.rb
+++ b/app/controllers/auth/confirmations_controller.rb
@@ -1,12 +1,18 @@
 # frozen_string_literal: true
 
 class Auth::ConfirmationsController < Devise::ConfirmationsController
+  include CaptchaConcern
+
   layout 'auth'
 
   before_action :set_body_classes
   before_action :set_pack
+  before_action :set_confirmation_user!, only: [:show, :confirm_captcha]
   before_action :require_unconfirmed!
 
+  before_action :extend_csp_for_captcha!, only: [:show, :confirm_captcha]
+  before_action :require_captcha_if_needed!, only: [:show]
+
   skip_before_action :require_functional!
 
   def new
@@ -15,8 +21,46 @@ class Auth::ConfirmationsController < Devise::ConfirmationsController
     resource.email = current_user.unconfirmed_email || current_user.email if user_signed_in?
   end
 
+  def show
+    old_session_values = session.to_hash
+    reset_session
+    session.update old_session_values.except('session_id')
+
+    super
+  end
+
+  def confirm_captcha
+    check_captcha! do |message|
+      flash.now[:alert] = message
+      render :captcha
+      return
+    end
+
+    show
+  end
+
   private
 
+  def require_captcha_if_needed!
+    render :captcha if captcha_required?
+  end
+
+  def set_confirmation_user!
+    # We need to reimplement looking up the user because
+    # Devise::ConfirmationsController#show looks up and confirms in one
+    # step.
+    confirmation_token = params[:confirmation_token]
+    return if confirmation_token.nil?
+    @confirmation_user = User.find_first_by_auth_conditions(confirmation_token: confirmation_token)
+  end
+
+  def captcha_user_bypass?
+    return true if @confirmation_user.nil? || @confirmation_user.confirmed?
+
+    invite = Invite.find(@confirmation_user.invite_id) if @confirmation_user.invite_id.present?
+    invite.present? && !invite.max_uses.nil?
+  end
+
   def set_pack
     use_pack 'auth'
   end
diff --git a/app/controllers/concerns/captcha_concern.rb b/app/controllers/concerns/captcha_concern.rb
new file mode 100644
index 0000000000..538c1ffb14
--- /dev/null
+++ b/app/controllers/concerns/captcha_concern.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+module CaptchaConcern
+  extend ActiveSupport::Concern
+  include Hcaptcha::Adapters::ViewMethods
+
+  included do
+    helper_method :render_captcha
+  end
+
+  def captcha_available?
+    ENV['HCAPTCHA_SECRET_KEY'].present? && ENV['HCAPTCHA_SITE_KEY'].present?
+  end
+
+  def captcha_enabled?
+    captcha_available? && Setting.captcha_enabled
+  end
+
+  def captcha_user_bypass?
+    false
+  end
+
+  def captcha_required?
+    captcha_enabled? && !captcha_user_bypass?
+  end
+
+  def check_captcha!
+    return true unless captcha_required?
+
+    if verify_hcaptcha
+      true
+    else
+      if block_given?
+        message = flash[:hcaptcha_error]
+        flash.delete(:hcaptcha_error)
+        yield message
+      end
+      false
+    end
+  end
+
+  def extend_csp_for_captcha!
+    policy = request.content_security_policy
+    return unless captcha_required? && policy.present?
+
+    %w(script_src frame_src style_src connect_src).each do |directive|
+      values = policy.send(directive)
+      values << 'https://hcaptcha.com' unless values.include?('https://hcaptcha.com') || values.include?('https:')
+      values << 'https://*.hcaptcha.com' unless values.include?('https://*.hcaptcha.com') || values.include?('https:')
+      policy.send(directive, *values)
+    end
+  end
+
+  def render_captcha
+    return unless captcha_required?
+
+    hcaptcha_tags
+  end
+end
diff --git a/app/helpers/admin/settings_helper.rb b/app/helpers/admin/settings_helper.rb
index baf14ab257..f99a2b8c8a 100644
--- a/app/helpers/admin/settings_helper.rb
+++ b/app/helpers/admin/settings_helper.rb
@@ -8,4 +8,8 @@ module Admin::SettingsHelper
     link = link_to t('admin.site_uploads.delete'), admin_site_upload_path(upload), data: { method: :delete }
     safe_join([hint, link], '<br/>'.html_safe)
   end
+
+  def captcha_available?
+    ENV['HCAPTCHA_SECRET_KEY'].present? && ENV['HCAPTCHA_SITE_KEY'].present?
+  end
 end
diff --git a/app/javascript/flavours/glitch/styles/forms.scss b/app/javascript/flavours/glitch/styles/forms.scss
index 3433abcddb..64d441fb25 100644
--- a/app/javascript/flavours/glitch/styles/forms.scss
+++ b/app/javascript/flavours/glitch/styles/forms.scss
@@ -1058,3 +1058,7 @@ code {
     display: none;
   }
 }
+
+.simple_form .h-captcha {
+  text-align: center;
+}
diff --git a/app/models/form/admin_settings.rb b/app/models/form/admin_settings.rb
index 3202d1fc24..34f14e3124 100644
--- a/app/models/form/admin_settings.rb
+++ b/app/models/form/admin_settings.rb
@@ -40,6 +40,7 @@ class Form::AdminSettings
     noindex
     outgoing_spoilers
     require_invite_text
+    captcha_enabled
   ).freeze
 
   BOOLEAN_KEYS = %i(
@@ -58,6 +59,7 @@ class Form::AdminSettings
     trendable_by_default
     noindex
     require_invite_text
+    captcha_enabled
   ).freeze
 
   UPLOAD_KEYS = %i(
diff --git a/app/views/admin/settings/edit.html.haml b/app/views/admin/settings/edit.html.haml
index b9daae8f05..49b03a9e35 100644
--- a/app/views/admin/settings/edit.html.haml
+++ b/app/views/admin/settings/edit.html.haml
@@ -42,7 +42,10 @@
 
   .fields-group
     = f.input :require_invite_text, as: :boolean, wrapper: :with_label, label: t('admin.settings.registrations.require_invite_text.title'), hint: t('admin.settings.registrations.require_invite_text.desc_html'), disabled: !approved_registrations?
-  .fields-group
+
+  - if captcha_available?
+    .fields-group
+      = f.input :captcha_enabled, as: :boolean, wrapper: :with_label, label: t('admin.settings.captcha_enabled.title'), hint: t('admin.settings.captcha_enabled.desc_html')
 
   %hr.spacer/
 
diff --git a/app/views/auth/confirmations/captcha.html.haml b/app/views/auth/confirmations/captcha.html.haml
new file mode 100644
index 0000000000..0f7cf9c595
--- /dev/null
+++ b/app/views/auth/confirmations/captcha.html.haml
@@ -0,0 +1,11 @@
+- content_for :page_title do
+  = t('auth.confirm_captcha')
+
+= form_tag auth_captcha_confirmation_url, method: 'POST', class: 'simple_form' do
+  = hidden_field_tag :confirmation_token, params[:confirmation_token]
+
+  .field-group
+    = render_captcha
+
+  .actions
+    %button.button= t('challenge.continue')
diff --git a/config/locales-glitch/en.yml b/config/locales-glitch/en.yml
index 5cc2625fc6..ab7f1b9766 100644
--- a/config/locales-glitch/en.yml
+++ b/config/locales-glitch/en.yml
@@ -2,6 +2,9 @@
 en:
   admin:
     settings:
+      captcha_enabled:
+        desc_html: Enable hCaptcha integration, requiring new users to solve a challenge when confirming their email address. This requires third-party scripts from hCaptcha to be embedded in the email verification page, which may have security and privacy concerns. Users that have been invited through a limited-use invite will not need to solve a CAPTCHA challenge.
+        title: Require new users to go through a CAPTCHA to confirm their account
       enable_keybase:
         desc_html: Allow your users to prove their identity via keybase
         title: Enable keybase integration
@@ -17,6 +20,8 @@ en:
       show_replies_in_public_timelines:
         desc_html: In addition to public self-replies (threads), show public replies in local and public timelines.
         title: Show replies in public timelines
+  auth:
+    confirm_captcha: User verification
   generic:
     use_this: Use this
   settings:
diff --git a/config/routes.rb b/config/routes.rb
index 65dd7ad638..d0eeda1e86 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -44,6 +44,7 @@ Rails.application.routes.draw do
       resource :setup, only: [:show, :update], controller: :setup
       resource :challenge, only: [:create], controller: :challenges
       get 'sessions/security_key_options', to: 'sessions#webauthn_options'
+      post 'captcha_confirmation', to: 'confirmations#confirm_captcha', as: :captcha_confirmation
     end
   end
 
diff --git a/config/settings.yml b/config/settings.yml
index 0942098226..7d192f3691 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -77,6 +77,7 @@ defaults: &defaults
   show_domain_blocks_rationale: 'disabled'
   outgoing_spoilers: ''
   require_invite_text: false
+  captcha_enabled: false
 
 development:
   <<: *defaults