The four Major tennis tournaments or Grand Slam tennis tournaments —sometimes called "championships", sometimes abbreviated "Tennis Majors" or even "Majors" or "Slams"— are the world's most important annual tennis tournaments. They are now most important by world tour ranking points, prize-money, strength and size of field, and public attention, and they have been considered most important for decades. January to September the Majors are the Australian Open, the French Open, Wimbledon (The Championships, Wimbledon), and the US Open. The Australian and US tournaments are currently played on hard courts, the French on clay, and Wimbledon on grass. Wimbledon is the oldest Major, founded in 1877, followed by the US in 1881, the French in 1891, and the Australian in 1905.

The tennis Grand Slam is a cumulative achievement, winning all four major championships in a single year in one of the five disciplines: men's and women's singles; men's, women's, and mixed doubles. In doubles one team may accomplish that playing together or one player may do it with different partners. The "Grand Slam" without qualification is winning the four majors in a single calendar year. That has been possible in all five disciplines every year since 1987, and in most years and most disciplines since the Australian Open was inaugurated in 1905.