The 2012 Western and Southern Open was a tennis tournament played on outdoor hard courts. It was the 111th edition (for the men) and the 84th (for the women) of the Cincinnati Masters, and was part of the ATP World Tour Masters 1000 of the 2012 ATP World Tour, and of the WTA Premier 5 tournaments of the 2012 WTA Tour. The tournament was held at the Lindner Family Tennis Center in Mason, Ohio, United States, from August 11 to August 19, 2012. Roger Federer and Li Na won the singles titles.

The following players were seeded in the main singles draw, following the ATP rankings of August 6, 2012:

The following players received wild cards into the main singles draw:

The following players received entry from the singles qualifying draw:

The following players received entry as lucky losers:

The following pairs received wildcards into the doubles main draw:

The following players received wild cards into the main singles draw:

The following players received entry from the singles qualifying draw: