Cool Ruler is a 1978 studio album by Gregory Isaacs, his first released on the Virgin Records subsidiary Front Line.

The Jamaican release was on Isaacs' African Museum imprint.

The album was produced by Isaacs and mixed by Lancelot "Maxie" McKenzie at Channel One Studios in Kingston, Jamaica.

Of the tracks on the album, "Let's Dance" had previously been released as a single.

Cool Ruler was reissued on compact disc by Virgin in 2000.