Klak
- Full Name: Klak
- Species: Klingon
- Gender: Male
- By 2266: First officer, Klingon Defense Force; IKS d'k tahg (TOS Novel: Errand of Vengeance: The Edge of the Sword)
- April 2, 2266: Captain, commanding officer, Klingon Defense Force; IKS d'k tahg (TOS Novel: Errand of Vengeance: Killing Blow)
- Death: April 2, 2266; IKS d'k tahg (TOS Novel: Errand of Vengeance: Killing Blow)
- Killed in challenge by first officer Koloth (TOS Novel: Errand of Vengeance: Killing Blow)