Porter Grainger (né Granger; October 22, 1891 − October 30, 1948) was an American pianist, songwriter, playwright, and music publisher. From 1924 to 1928, he worked with blues singer Bessie Smith to record more than a dozen sides for Columbia Records. Amongst the height of his career was the 1928 stage production, Mississippi Days, which also featured Smith. He was also Mamie Smith's accompanist in the 1929 film short Jailhouse Blues and regularly appeared with her in stage shows.
Two of Grainger's songs have endured as blues standards: "Tain't Nobody's Biz-iness If I Do" (co-authored with Everett Robbins, who had also played piano in Mamie Smith's Jazz Hounds), and "Dying Crapshooter's Blues" (1927).