A tennis shirt, often referred to in the popular culture as a polo shirt, is a T-shaped shirt with a collar and two buttons; occasionally they also include a pocket. Common fabrics for these shirts include pique cotton, jersey cotton, or pima cotton.

Sometimes a tennis shirt's cloth is cut so that the back hangs a few centimeters lower than the front. This is called a tennis tail. The original 1929 design by tennis player Rene Lacoste called for a thick pique collar that one would wear turned up in order to block the sun from one's neck.

During the 1990's, the tennis shirt became the standard informal business attire for the high tech industry. In the People's Republic of China, most younger government officials wear a tennis shirt (sometimes made of silk) as standard business attire.