2017 Western & Southern Open – Men's singles

Grigor Dimitrov defeated Nick Kyrgios in the final, 6–3, 7–5 to win the men's singles tennis title at the 2017 Cincinnati Masters. It was his first Masters 1000 title, and he did not lose a set en route.

Marin Čilić was the reigning champion, but did not participate.

Given the withdrawals of Novak Djokovic, Andy Murray, and Roger Federer (all due to injury), Rafael Nadal was the only member of the Big Four to play. His loss in the quarterfinals to Kyrgios ended a streak of 42 consecutive Masters 1000 events where at least one of the four reached the final (also winning a combined 37 titles). Nonetheless, Nadal regained the world No. 1 singles ranking for the first time since July 2014. Nadal became the world No. 1 with only 7,645 ranking points, the fewest points for an ATP No. 1 since the establishment of a new ranking points distribution in 2009.

Seeds
The top eight seeds receive a bye into the second round. • 🇪🇸 Rafael Nadal (quarterfinals)

• Roger Federer (withdrew)

• 🇦🇹 Dominic Thiem (quarterfinals)

• 🇩🇪 Alexander Zverev (second round)

• 🇯🇵 Kei Nishikori (withdrew)

• 🇨🇦 Milos Raonic (withdrew)

• 🇧🇬 Grigor Dimitrov (champion)

• 🇫🇷 Jo-Wilfried Tsonga (second round)

• 🇧🇪 David Goffin (first round)

• 🇨🇿 Tomáš Berdych (first round)

• 🇪🇸 Pablo Carreño Busta (third round)

• 🇪🇸 Roberto Bautista Agut (first round)

• 🇺🇸 Jack Sock (first round)

• 🇺🇸 John Isner (semifinals)

• 🇺🇸 Sam Querrey (second round)

• 🇱🇺 Gilles Müller (second round)

Seeds
• # João Sousa (qualified)

• # 🇷🇺 Andrey Rublev (first round)

• # 🇷🇸 Janko Tipsarević (qualifying competition, lucky loser)

• # 🇷🇸 Dušan Lajović (first round)

• # 🇺🇦 Alexandr Dolgopolov (qualified)

• # 🇨🇦 Vasek Pospisil (first round)

• # 🇹🇳 Malek Jaziri (first round)

• # 🇺🇿 Denis Istomin (first round)

• # 🇺🇸 Ernesto Escobedo (first round)

• # 🇫🇷 Julien Benneteau (first round)

• # 🇮🇹 Thomas Fabbiano (qualifying competition, lucky loser)

• # 🇷🇺 Mikhail Youzhny (qualified)

• # 🇺🇸 Bjorn Fratangelo (first round)

• # 🇩🇪 Maximilian Marterer (qualified)

Qualifiers
• # João Sousa

• # 🇷🇺 Mikhail Youzhny

• # 🇺🇸 Christopher Eubanks

• # 🇩🇪 Maximilian Marterer

• # 🇺🇦 Alexandr Dolgopolov

• # 🇦🇺 John-Patrick Smith

• # 🇺🇸 Mitchell Krueger

Lucky losers
• # 🇷🇸 Janko Tipsarević

• # 🇮🇹 Thomas Fabbiano

• # 🇮🇳 Ramkumar Ramanathan

• # 🇺🇸 Christian Harrison