The 2021 Cleveland Open was a professional tennis tournament played on hard courts. It was the third edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Cleveland, Ohio, United States between March 15 and March 21, 2021.^[1]

Country	Player1	Rank1	Seed
AUS	James Duckworth	103	1
JPN	Go Soeda	144	2
ECU	Emilio Gómez	176	3
DEN	Mikael Torpegaard	190	4
USA	Mitchell Krueger	205	5
CAN	Brayden Schnur	216	6
USA	Thai-Son Kwiatkowski	218	7
DOM	Roberto Cid Subervi	231	8

• ¹ Rankings are as of 8 March 2021.^[2]

The following players received wildcards into the singles main draw:

• Liam Draxl
• Roy Smith
• Zachary Svajda

The following players received entry into the singles main draw as alternates:

• Lucas Catarina
• Evan King
• Nicolás Mejía

The following players received entry from the qualifying draw:

• Felix Corwin
• Alexis Galarneau
• Aleksandar Kovacevic
• Evan Song

• Bjorn Fratangelo def. Jenson Brooksby 7–5, 6–4.

• Robert Galloway / Alex Lawson def. Evan King / Hunter Reese 7–5, 6–7^(5–7), [11–9].