The 2021 Split Open was a professional tennis tournament played on clay courts. It was part of the 2021 ATP Challenger Tour. It took place in Split, Croatia between 5 and 11 April 2021.

Country	Player	Rank1	Seed
POR	Pedro Sousa	111	1
AUS	Marc Polmans	137	2
AUT	Sebastian Ofner	152	3
EGY	Mohamed Safwat	159	4
SRB	Danilo Petrović	160	5
SLO	Blaž Rola	166	6
BEL	Kimmer Coppejans	170	7
SVK	Filip Horanský	175	8

• Rankings are as of 22 March 2021.^[1]

The following players received wildcards into the singles main draw:

• Duje Ajduković
• Mili Poljičak
• Nino Serdarušić

The following players received entry into the singles main draw using protected rankings:

• Dustin Brown
• Thanasi Kokkinakis

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

• Zdeněk Kolář

The following player received entry into the singles main draw as an alternate:

• Kacper Żuk

The following players received entry from the qualifying draw:

• Mirza Bašić
• Uladzimir Ignatik
• Blaž Kavčič
• Akira Santillan

• Blaž Rola def. Blaž Kavčič 2–6, 6–3, 6–2.

• Andrey Golubev / Aleksandr Nedovyesov def. Szymon Walków / Jan Zieliński 7–5, 6–7^(5–7), [10–5].