2021 San Marino Open

The 2021 San Marino Open was a professional tennis tournament played on clay courts. The 28th edition of the tournament, which was part of the 2021 ATP Challenger Tour, took place in City of San Marino, San Marino between 9 and 15 August 2021.

Seeds

 * 1 Rankings are as of 2 August 2021.

Other entrants
The following players received wildcards into the singles main draw:
 * 🇮🇹 Raúl Brancaccio
 * 🇸🇲 Marco De Rossi
 * 🇮🇹 Luca Nardi

The following player received entry into the singles main draw using a protected ranking:
 * 🇧🇪 Julien Cagnina

The following player received entry into the singles main draw as an alternate:
 * 🇹🇳 Malek Jaziri

The following players received entry from the qualifying draw:
 * 🇮🇹 Francesco Forti
 * 🇧🇷 Orlando Luz
 * 🇮🇹 Manuel Mazza
 * 🇮🇹 Julian Ocleppo

The following player received entry as a lucky loser:
 * 🇷🇺 Pavel Kotov

Singles

 * Holger Rune def. 🇧🇷 Orlando Luz 1–6, 6–2, 6–3.

Doubles

 * 🇨🇿 Zdeněk Kolář / 🇻🇪 Luis David Martínez def. 🇧🇷 Rafael Matos / 🇧🇷 João Menezes 1–6, 6–3, [10–3].