Roughly a year after proposing at Pelican Hill in Newport Coast, California, married his wife, Hannah, on May 21, 2023 in Mesa, Arizona, a little over 10 miles northwest of Scottsdale, where the 2023 NCAA Championship was contested at Grayhawk Golf Club from May 26-31.

He and his wife attended rival high schools in California (Ontario Christian for William, Western Christian for Hannah) and met after one of William’s basketball games their junior years.

Favorite sports team is the Phoenix Suns (NBA).

Taught himself to juggle eggs by first juggling golf balls; he was bored at school one day, found a how-to video on YouTube, pulled a couple golf balls out of his bag and taught himself to juggle within a half hour.

Also taught himself to ride a unicycle over the course of two weeks in middle school.

Parents, Billy and Michelle Mouw, own and operate Billy’s Egg Farm in the family’s hometown of Chino, California roughly 35 miles east of Los Angeles; they celebrated their 30th year in business in 2022.

Teammates at Pepperdine University included Sahith Theegala (2019-20 season), Clay Feagler (2019-21), RJ Manke (2019-21), and Joe Highsmith (2019-22).

Finished No. 6 in the 2023 PGA TOUR University Ranking, earning conditional Korn Ferry Tour membership for the remainder of 2023, along with an exemption to Second Stage of 2023 PGA TOUR Q-School presented by Korn Ferry, fully exempt status on PGA TOUR Canada for 2023, and exempt status through the Latin America Swing of the 2024 PGA TOUR Americas season.

Played four seasons at Pepperdine University (2019-23) in Malibu, California, less than 30 miles west of Los Angeles. Collegiate highlights included two All-America selections (First Team for 2019-20 season, Third Team for 2022-23 season), helping the Waves win the team national title at the 2021 NCAA Championship, earning the 2022-23 West Coast Conference Co-Player of the Year award, and notching one individual victory.

Finished his career ranked third in program history in career scoring average (71.00), only trailing Sahith Theegala (70.61 from 2016-20)) and Dylan Menante (70.98 from 2020-22).

Went 1-1-1 in match play as he helped Pepperdine win the 2021 NCAA Championship, the program’s first national title since Jason Gore led the 1997 Waves to the title; he lost a quarterfinal match to Florida State’s John Pak, halved a semifinal with Oklahoma State’s Bo Jin, and defeated Oklahoma’s Quade Cummins in the final.

Recorded one of the best seasons in program history en route to a 2019-20 All-America First Team honor as a freshman; his scoring average of 69.96 across 24 rounds ranked second in school history, only behind Sahith Theegala’s 69.04 across 24 rounds that same season. The duo, along with future Korn Ferry Tour members Clay Feagler, Joe Highsmith and RJ Manke, helped Pepperdine reach No. 1 during the regular season for the first time in program history prior to the season ending prematurely as a result of the COVID-19 pandemic.

Helped Pepperdine win back-to-back WCC Championships in 2021 and 2022, including a record-shattering 54-hole team score of 49-under 815 en route to the 2021 title; they broke the previous record of 26-under 838 set by the 2018 Waves.

Represented the United States at the 2021 Walker Cup at Seminole Golf Club, and was named to the 2020 Arnold Palmer Cup team but was a late withdrawal and did not compete.

Won the 2022 Trans-Mississippi Amateur Championship at Denver Country Club, joining past winners Pierceson Coody (2019), Will Zalatoris (2014 and 2016), Collin Morikawa (2015), Ben Crenshaw (1972), and Jack Nicklaus (1958 and 1959).

Semifinalist at the 2022 Western Amateur, where he lost to Austin Greaser.

Played in five consecutive U.S. Amateur Championships from 2018 through 2022, with the highlights being Round of 16 appearances in 2018 and 2020.

Won the 2019 California State Amateur Championship at Monterey Peninsula Country Club at age 18, becoming one of the youngest winners in the event’s history and joining past winners Xander Schauffele (2014), Spencer Levin (2004), Jason Gore (1997), Mark O’Meara (1979), Johnny Miller (1968), and Ken Venturi (1951, 1956).

Won the 2017 Western Junior Championship by eight strokes, tied for the largest margin of victory in the event’s history, over runner-up Karl Vilips; he tied the 72-hole tournament scoring record of 266 previously established by Hunter Mahan in 1999.