William Henry Sadler IV (born September 21, 1981) is a former right-handed relief pitcher.

[2] He led LSU with four saves, but took the loss when the Tigers were eliminated from the 2003 College World Series by the University of South Carolina.

Between Connecticut and Fresno, he struck out 78 batters in 54+2⁄3 innings while holding opponents to a .148 batting average.

[2] Sadler's minor league success in 2006 earned him a spot on the Giants' September expanded roster when Armando Benítez was placed on the 60-day disabled list.

Sadler was with the Giants in spring training in 2007, but struggled with his control and was optioned to Fresno March 18.