Fowles received 31 votes from the 49-member panel of sportswriters and broadcasters. Los Angeles guard Brittney Sykes was second (six votes), and Connecticut forward Jonquel Jones and Phoenix forward Brianna Turner tied for third with four votes each.
Phoenix center Brittney Griner received two votes, and Connecticut guards Briann January and Jasmine Thomas received one each.
Only one player has earned the Defensive Player of the Year honor more than Fowles: former Indiana forward Tamika Catchings, who retired in 2016 after winning the award five times.
Fowles will lead third-seeded Minnesota against the No. 6-seeded Chicago Sky in a WNBA second-round playoff game Sunday (5 p.m. ET, ESPN2).
The WNBA also named its All-Defensive teams Sunday. Fowles, Sykes, Jones, Turner and January were on the first team. Griner, Thomas, Connecticut's Brionna Jones, Washington's Ariel Atkins and Seattle's Breanna Stewart were on the second team.
In all, No. 1 seed Connecticut, the top defensive squad this season, holding teams to just under 70 points per game, had four players named all-defense.
The 6-foot-6 Fowles, who was the No. 2 draft pick in 2008 out of LSU, is second in the league this season in steals and blocked shots (1.8 per game for both categories). She is third in defensive rebounds (8.0 per game) and second in overall rebounds (10.1).
Fowles, who turns 36 next month, is used to playing a big role defensively.
"That was embedded in me at an early age," she said. "I can definitely say this team challenged me to do more -- not in a bad way, but just to make sure I'm aware of a lot of things."
Lynx coach Cheryl Reeve agreed that a younger squad has had to rely on Fowles more than ever. Fowles also is second in scoring for Minnesota at 16.0 points per game.
"We give her great responsibility," Reeve said. "She's not just guarding her player. She's the one that's coming to help on drives."
Fowles previously won the DPOY award in 2011 and 2013, when she was with Chicago, and in 2016 with Minnesota. She was the league MVP in 2017 and the WNBA Finals MVP in 2015 and 2017.
"I think what stands out to me on the court is not only her deflections, blocks and steals, it's what she does even off the ball," Lynx teammate Bridget Carleton said of Fowles. "She's always there to help. She's so versatile at the defensive end, and it's not just because of her size. She moves her feet so well, and it seems like she's everywhere."