The 2023 Keio Challenger was a professional tennis tournament played on hard courts. It was the 16th (men's) and 6th (women's) editions of the tournament and part of the 2023 ATP Challenger Tour and the 2023 ITF Women's World Tennis Tour. It took place in Yokohama, Japan between 20 November and 3 December 2023.
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw as an alternate:
The following players received entry from the qualifying draw:
The following players received entry as lucky losers:
