William Endfield Steinberg (born February 26, 1950) is an American songwriter. He achieved his greatest success in the 1980s with songwriting partner Tom Kelly; together they two wrote or co-wrote the No. 1 hits "Like a Virgin" by Madonna (1984), "True Colors" by Cyndi Lauper (1986), "Eternal Flame" by the Bangles (1989), "So Emotional" by Whitney Houston (1987) and "Alone" (covered by Heart in 1987). They also wrote or co-wrote the hit songs "I Drove All Night" (recorded by various artists, 1987), "I Touch Myself" by Divinyls (1990), and "I'll Stand By You" by The Pretenders (1994).
After Kelly retired from music in the 1990s, Steinberg collaborated with other songwriters. With Rick Nowels and Marie-Claire D'Ubaldo he wrote the hit songs "Falling Into You" (covered by Celine Dion) and "One & One". He has written hit songs with Josh Alexander including "All About Us" by t.A.T.u. (2005), "Too Little Too Late" by JoJo (2006) and "Give Your Heart a Break" by Demi Lovato (2012).