Ogwumike shot 11 of 15 from the field and hit a career-high five 3-pointers and Gray finished with 13 points, a career-best 10 rebounds and 13 assists. It was just the eighth regular-season triple-double in WNBA history, and ninth overall.
Elena Delle Donne, Washington's leading scorer (17.2 points per game) this season, left the game in the first minute with a facial injury and did not return.
Riquna Williams added 19 points, including five 3s, and Tierra Ruffin-Pratt scored 12 for Los Angeles (7-6).
Ogwumike hit a 3-pointer to make it 10-7 midway through the first quarter and the Sparks led the rest of the way. She finished the quarter with four 3-pointers -- matching her previous career high -- and 14 points, and Williams scored 10, as L.A. took a 29-21 lead into the second.
The Sparks led 51-46 lead at the break, scoring their most points in a half this season, and finished with a season-high 15 3s on 30 attempts.
Aerial Powers led the Mystics (9-4) with a career-high 24 points and Kristi Tolliver had 18 points and nine rebounds. The Mystics had their five-game win streak snapped.
Delle Donne leaves game after face injury
After the opening minute of the Mystics' game vs. the Sparks, Elena Delle Donne leaves with a facial injury and doesn't return.