First released by P.P. Arnold (UK #18 1967).
Also recorded by Cat Stevens, writer (1967).
Other hit versions by Norma Frazier (Jamaica, 1967), Keith Hampshire (CAN #1 1973), Rod Stewart (US #21/UK #1 1976), Sheryl Crow (US #14/MOR #1 2003).
From the wiki: “‘The First Cut Is the Deepest’ is a 1967 song written by Cat Stevens, originally released by P. P. Arnold in the spring of 1967. Stevens had made a demo recording of ‘The First Cut Is the Deepest’ in 1965 but had written the song only to promote his songwriting to other artists, and did not record it for commercial release until early October 1967. He sold the song for £30 to P. P. Arnold and it became a huge hit for her in the UK, reaching #18 on the UK Singles Chart.