2018 Keio Challenger

The 2018 Keio Challenger was a professional tennis tournament played on hard courts. It was the thirteenth and second editions of the tournament and part of the 2018 ATP Challenger Tour and the 2018 ITF Women's Circuit. It took place in Yokohama, Japan between 26 February and 4 March 2018 for the men's edition and between 5 and 11 March 2018 for the women's.

Men's singles main-draw entrants

¹ Rankings are as of 19 February 2018.

The following players received wildcards into the singles main draw:

The following player received entry into the singles main draw as a special exempt:

The following players received entry from the qualifying draw:

The following player received entry as a lucky loser:

¹ Rankings are as of 26 February 2018.

The following players received wildcards into the singles main draw:

The following players received entry from the qualifying draw:

Yasutaka Uchiyama def. Tatsuma Ito 2–6, 6–3, 6–4.

Veronika Kudermetova def. Harriet Dart, 6–2, 6–4

Tobias Kamke / Tim Pütz def. Sanchai Ratiwatana / Sonchat Ratiwatana 3–6, 7–5, .

Laura Robson / Fanny Stollár def. Momoko Kobori / Chihiro Muramatsu, 5–7, 6–2,