A grass court is one of the four different types of tennis court on which the sport of tennis, originally known as "lawn tennis", is played. Grass courts are made of grasses in different compositions depending on the tournament.
Although grass courts are more traditional than other types of tennis courts, maintenance costs of grass courts are higher than those of hard courts and clay courts. Grass courts (in the absence of suitable covers) must be left for the day if rain appears, as the grass becomes very slippery when wet.
Grass courts are most common in Britain, although the Northeastern United States also has some private grass courts.
Because grass courts tend to be slippery, the ball often skids and bounces low while retaining most of its speed, rarely rising above knee height. In addition, there are often bad bounces. As a result, players must reach the ball faster relative to other surfaces, and rallies are likely to be comparatively brief; therefore, speed and power are rewarded on grass. On grass, the serve and return play a major part in determining the outcome of the point, increasing the importance of serving effectively, and maintaining focus in exchanges which can be heavily influenced by lapses in concentration. A grass-court favours a serve and volley style of play.