Cincinnati is a Masters 1000 event on the ATP World Tour meaning all Top 44 men are required to play.
The event is a Premier 5 WTA women's event.
*Williams has entered with a protected ranking of No. 1, the ranking she held prior to stepping away from tennis in early 2017 before giving birth to her daughter last September.
Note: Rankings are as of the entry deadline, July 2. Commitment list does not include all wild cards and qualifiers.