The high-flying denial came with 4:45 remaining in the first quarter of the Pacers' 120-95 victory on Sunday at Bankers Life Fieldhouse in Indianapolis.
Williams had the ball out beyond the 3-point arc on the play. He dribbled into the paint past Pacers forward Thaddeus Young before taking flight. Williams went up strong with one hand and appeared to have a clear path to the rim, but Turner was waiting.
The 6-foot-11 center timed his jump perfectly and went up with his right hand, swatting the ball away from Williams and sending him crashing to the floor.
"It was up there," Turner told reporters. "It was a good block. I met him at the rim. It's something I expect for myself."
Williams scored nine points in the loss.
The Pacers host the Toronto Raptors at 7 p.m. on Wednesday in Indianapolis.