Marc Okrand was commissioned by Paramount Pictures to develop a Klingon language; the language he created was tlhIngan Hol. He has translated Klingon dialogue for the feature films Star Trek III: The Search for Spock, Star Trek V: The Final Frontier, Star Trek VI: The Undiscovered Country, Star Trek (deleted scenes) and Star Trek Into Darkness, as well as episodes of Star Trek: The Next Generation and Star Trek: Enterprise.
Many Klingon-speakers consider him to be the final authority on tlhIngan Hol, and will not accept words or grammar that he has not approved, regardless of whether or not they appear in any licensed Star Trek media.
- The Klingon Dictionary
- Klingon for the Galactic Traveler
- The Klingon Way
- Conversational Klingon
- Power Klingon
- HolQeD (various articles)
- Diplomatic Implausibility (vetted the book's Klingon glossary)
- Sarek (Klingon language assistance)
- Star Trek: Klingon (creative consultant and Klingon voiceover)
- Klingon Bird of Prey Owners' Workshop Manual (Klingon translations)
- Talk Now! Learn Klingon (Klingon translations)
- Star Trek Klingon Edition Monopoly (Klingon translations)
- SkyBox trading cards (Klingon translations for several cards)
- Klingon Bird-of-Prey cutaway poster by SciPubTech (Klingon translation)