diff --git a/lib/rouge/demos/ttcn3 b/lib/rouge/demos/ttcn3
new file mode 100644
index 0000000000..969107de42
--- /dev/null
+++ b/lib/rouge/demos/ttcn3
@@ -0,0 +1,6 @@
+module DNSTester {
+  type integer Identification( 0..65535 ); // 16-bit integer
+  type enumerated MessageKind {e_Question, e_Answer};
+  type charstring Question;
+  type charstring Answer;
+}
diff --git a/lib/rouge/lexers/ttcn3.rb b/lib/rouge/lexers/ttcn3.rb
new file mode 100644
index 0000000000..4b8b27d35c
--- /dev/null
+++ b/lib/rouge/lexers/ttcn3.rb
@@ -0,0 +1,119 @@
+# -*- coding: utf-8 -*- #
+# frozen_string_literal: true
+
+module Rouge
+  module Lexers
+    class TTCN3 < RegexLexer
+      title "TTCN3"
+      desc "The TTCN3 programming language (ttcn-3.org)"
+
+      tag 'ttcn3'
+      filenames '*.ttcn', '*.ttcn3'
+      mimetypes 'text/x-ttcn3', 'text/x-ttcn'
+
+      def self.keywords
+        @keywords ||= %w(
+          module import group type port component signature external
+          execute const template function altstep testcase var timer if
+          else select case for while do label goto start stop return
+          break int2char int2unichar int2bit int2enum int2hex int2oct
+          int2str int2float float2int char2int char2oct unichar2int
+          unichar2oct bit2int bit2hex bit2oct bit2str hex2int hex2bit
+          hex2oct hex2str oct2int oct2bit oct2hex oct2str oct2char
+          oct2unichar str2int str2hex str2oct str2float enum2int
+          any2unistr lengthof sizeof ispresent ischosen isvalue isbound
+          istemplatekind regexp substr replace encvalue decvalue
+          encvalue_unichar decvalue_unichar encvalue_o decvalue_o
+          get_stringencoding remove_bom rnd hostid send receive
+          setverdict
+        )
+      end
+
+      def self.reserved
+        @reserved ||= %w(
+          all alt apply assert at configuration conjunct const control
+          delta deterministic disjunct duration fail finished fuzzy from
+          history implies inconc inv lazy mod mode notinv now omit
+          onentry onexit par pass prev realtime seq setstate static
+          stepsize stream timestamp until values wait
+        )
+      end
+
+      def self.types
+        @types ||= %w(
+          anytype address boolean bitstring charstring hexstring octetstring
+          component enumerated float integer port record set of union universal
+        )
+      end
+
+      # optional comment or whitespace
+      ws = %r((?:\s|//.*?\n|/[*].*?[*]/)+)
+      id = /[a-zA-Z_]\w*/
+      digit = /\d_+\d|\d/
+      bin_digit = /[01]_+[01]|[01]/
+      oct_digit = /[0-7]_+[0-7]|[0-7]/
+      hex_digit = /\h_+\h|\h/
+
+      state :statements do
+        rule %r/\n+/m, Text
+        rule %r/[ \t\r]+/, Text
+        rule %r/\\\n/, Text # line continuation
+
+        rule %r(//(\\.|.)*?$), Comment::Single
+        rule %r(/(\\\n)?[*].*?[*](\\\n)?/)m, Comment::Multiline
+
+        rule %r/"/, Str, :string
+        rule %r/'(?:\\.|[^\\]|\\u[0-9a-f]{4})'/, Str::Char
+        
+        rule %r/#{digit}+\.#{digit}+([eE]#{digit}+)?[fd]?/i, Num::Float
+        rule %r/'#{bin_digit}+'B/i, Num::Bin
+        rule %r/'#{hex_digit}+'H/i, Num::Hex
+        rule %r/'#{oct_digit}+'O/i, Num::Oct
+        rule %r/#{digit}+/i, Num::Integer
+
+        rule %r([~!%^&*+:=\|?<>/-]), Operator
+        rule %r/[()\[\]{},.;:]/, Punctuation
+
+        rule %r/(?:true|false|null)\b/, Name::Builtin
+
+        rule id do |m|
+          name = m[0]
+          if self.class.keywords.include? name
+            token Keyword
+          elsif self.class.types.include? name
+            token Keyword::Type
+          elsif self.class.reserved.include? name
+            token Keyword::Reserved
+          else
+            token Name
+          end
+        end
+      end
+
+      state :root do
+        rule %r/module\b/, Keyword::Declaration, :module
+        rule %r/import\b/, Keyword::Namespace, :import
+
+        mixin :statements
+      end
+
+      state :string do
+        rule %r/"/, Str, :pop!
+        rule %r/\\([\\abfnrtv"']|x[a-fA-F0-9]{2,4}|[0-7]{1,3})/, Str::Escape
+        rule %r/[^\\"\n]+/, Str
+        rule %r/\\\n/, Str
+        rule %r/\\/, Str # stray backslash
+      end
+
+      state :module do
+        rule %r/\s+/m, Text
+        rule id, Name::Class, :pop!
+      end
+
+      state :import do
+        rule %r/\s+/m, Text
+        rule %r/[\w.]+\*?/, Name::Namespace, :pop!
+      end
+    end
+  end
+end
diff --git a/spec/lexers/ttcn3_spec.rb b/spec/lexers/ttcn3_spec.rb
new file mode 100644
index 0000000000..1acad980f1
--- /dev/null
+++ b/spec/lexers/ttcn3_spec.rb
@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*- #
+# frozen_string_literal: true
+
+describe Rouge::Lexers::TTCN3 do
+  let(:subject) { Rouge::Lexers::TTCN3.new }
+
+  describe 'guessing' do
+    include Support::Guessing
+
+    it 'guesses by filename' do
+      assert_guess :filename => 'foo.ttcn'
+      assert_guess :filename => 'foo.ttcn3'
+    end
+
+    it 'guesses by mimetype' do
+      assert_guess :mimetype => 'text/x-ttcn'
+      assert_guess :mimetype => 'text/x-ttcn3'
+    end
+  end
+end
diff --git a/spec/visual/samples/ttcn3 b/spec/visual/samples/ttcn3
new file mode 100644
index 0000000000..034926f0d9
--- /dev/null
+++ b/spec/visual/samples/ttcn3
@@ -0,0 +1,120 @@
+/* ----------------------------------------------------------------------------
+ * (c) Copyright Wiley & Sons 2005
+ *
+ * @author: Colin Willcock, Thomas Deiß, Stephan Tobies, Stefan Keil, Federico 
+ *          Engler, Stephan Schulz
+ * @desc:   This is a strongly simplified Domain Name Server (DNS) test suite  
+ *          for testing some basic domain name resolution behaviour.
+ * @remark: This TTCN-3 code is based on the DNS example code presented in 
+ *          "C. Willock et al., An Introduction to TTCN-3, Wiley & Sons, 2005. 
+ *          ISBN: 0-470-01224-2"
+ *          This copyright notice shall not be removed in copies of this file.
+ * ----------------------------------------------------------------------------
+*/
+module DNSTester {
+
+  // Simple type definitions to match the protocol structure
+  type integer Identification( 0..65535 ); // 16-bit integer
+  type enumerated MessageKind {e_Question, e_Answer};
+  type charstring Question;
+  type charstring Answer;
+
+  // The definition of our DNS message type.
+  type record DNSMessage {
+    Identification identification,
+    MessageKind messageKind,
+    Question question,
+    Answer answer optional
+  }
+
+  // A possible template for the DNS message type.
+  template DNSMessage a_NokiaQuestion := {
+    identification := 12345,
+    messageKind := e_Question,
+    question := "www.nokia.com",
+    answer := omit
+  }
+
+  // A parameterized template for DNS questions based on DNSMessage.
+  template DNSMessage a_DNSQuestion( Identification p_id, Question p_question ) := {
+    identification := p_id,
+    messageKind := e_Question,
+    question := p_question,
+    answer := omit
+  }
+
+  // A parameterized template for DNS answers based on DNSMessage.
+  template DNSMessage a_DNSAnswer( Identification p_id, Answer p_answer ) := {
+    identification := p_id,
+    messageKind := e_Answer,
+    question := ?,
+    answer := p_answer
+  }
+
+  // DNS messages are allowed to move in and out through ports of this type.
+  type port DNSPort message {
+    inout DNSMessage
+  }
+
+  // Our single component uses one single port to communicate with the SUT.
+  type component DNSClient {
+    port DNSPort serverPort
+  }
+
+  // Our first test case! This small test case will behave very poorly in case
+  // of an erroneous SUT. More about this later!
+  testcase ExampleResolveNokia1() runs on DNSClient {
+    serverPort.send( a_DNSQuestion( 12345, "www.research.nokia.com" ) );
+    serverPort.receive( a_DNSAnswer( 12345, "172.21.56.98" ) );
+    setverdict( pass );
+    stop;
+  }
+
+  testcase ExampleResolveNokia2() runs on DNSClient {
+    serverPort.send( a_DNSQuestion( 12345, "www.research.nokia.com" ) );
+    alt {
+      // Handle the case when the expected answer comes in.
+      [] serverPort.receive( a_DNSAnswer( 12345, "172.21.56.98" ) ) {
+         setverdict( pass );
+      }
+      // Handle the case when unexpected answers come in.
+      [] serverPort.receive {
+         setverdict( fail );
+      }
+    }
+    stop;
+  }
+
+  // Our test case is now able to handle incorrect replies as well as
+  // missing replies.
+  testcase ExampleResolveNokia3() runs on DNSClient {
+    timer replyTimer;
+    serverPort.send( a_DNSQuestion( 12345, "www.research.nokia.com" ) );
+    replyTimer.start( 20.0 );
+    alt {
+      // Handle the case when the expected answer comes in.
+      [] serverPort.receive( a_DNSAnswer( 12345, "172.21.56.98" ) ) {
+         setverdict( pass );
+         replyTimer.stop;
+      }
+      // Handle the case when unexpected answers come in.
+      [] serverPort.receive {
+         setverdict( fail );
+         replyTimer.stop;
+      }
+      // Handle the case when no answer comes in.
+      [] replyTimer.timeout {
+         setverdict( fail );
+      }
+    }
+    stop;
+  }
+
+  // Our small control part.
+  control {
+    execute( ExampleResolveNokia1() );
+    execute( ExampleResolveNokia2() );
+    execute( ExampleResolveNokia3() );
+  }
+
+}