Fafhrd and Gray Mouser #1-4 (1991)
In 1972, Fafhrd and the Mouser began their comics career, appearing in Wonder Woman #202 alongside the title character and Catwoman in a story scripted by award-winning SF writer Samuel R. Delany.
In 1973, DC Comics began an ongoing series, Sword of Sorcery, featuring the duo. The title was written by Denny O'Neil and featured art by Howard Chaykin, Walt Simonson and Jim Starlin; the well-received title ran only five issues. Stories included adaptations of "The Price of Pain-Ease", "Thieves' House", "The Cloud of Hate", and "The Sunken Land", as well as original stories.
In 1991, Epic Comics published a four-issue comic book adaptation of seven of the stories: "Ill Met in Lankhmar" (issue 1), "The Circle Curse" and "The Howling Tower" (issue 2), "The Price of Pain Ease" and "Bazaar of the Bizarre" (issue 3), and "Lean Times in Lankhmar" and "When the Sea King's Away" (issue 4). The comics were scripted by Howard Chaykin, who had drawn several issues of the earlier DC title, and pencilled by Mike Mignola, whose Hellboy comic book often has a similar feel to Leiber's work. Mignola also did the jacket covers and interior art for the White Wolf collection. This series was collected by Dark Horse Comics in a trade paperback collection published in March 2007.
Marvel Comics created their own version of Fafhrd and the Gray Mouser, when they introduced the Vanir Fafnir and his companion Blackrat to the Conan comics. The pairs of characters were very much alike and Roy Thomas, who wrote the original Conan comics, made no secret that it was his intention to create characters that were a tribute to Fritz Leiber's creations.
If you liked these stories, please check out the 1973 Sword of Sorcery series here:
Props to Samm and Was for the scans.