In the Key of Lightnin' is an album by blues musician Lightnin' Hopkins, recorded at the sessions that produced Lightnin'!

in California in 1969, but not released until 2002 on the Tomato label.

[2] The Penguin Guide to Blues Recordings said: "In the Key of Lightnin' contains unissued material from the Poppy sessions with the full band on "What'd I Say" and "Katie May".

Five tracks are snatches of inconsequential talking".

[3] All compositions by Sam "Lightnin'" Hopkins except where noted