Williams won the first five games of the match but then dropped the second set before rebounding and upending her Polish opponent 6-1, 5-7, 6-2.
The win put Williams back on top in the tournament she won in 2002, 2003, 2009 and 2010, drawing her even with her older sister, Venus, who won the title in 2000, 2001, 2005, 2007 and 2008.
Williams employed a solid serve, which averaged 107 miles per hour, to turn back the determined Radwanska. Williams won 82 percent of her points when she got her first serve in. She served 17 aces to two for Radwanska, which helped overcome 36 unforced errors.
Radwanska, who was seeking her first Grand Slam title, won 61 percent of her first-serve points. She was the first Polish player to play in a major title match since 1939.