Williams became the oldest player to win a WTA singles match since 2004 when she beat Peyton Stearns at last month's Washington Open after a 16-month absence from competitive tennis.
She last played in the US Open singles main draw in 2023, losing in the first round to Belgian Greet Minnen.
The seven-time Grand Slam winner is also playing in the tournament's new-look mixed doubles tournament with compatriot Reilly Opelka.
Other women's singles wildcards included France's Caroline Garcia, in what will likely be the 2022 semi-finalist's last appearance at Flushing Meadows.
The 2022 WTA Finals winner announced plans to retire from the sport earlier this year.
