Over-the-line is a bat-and-ball sport, a game related to baseball and softball. Like those games, you have the batter, pitcher, and fielders. Because a game requires only three people per team, it is considerably easier to get a good informal game going. Equipment consists of a rope (or lines marked in the sand), an "official" softball bat and a rubber softball. No ball gloves are allowed except in women's games, however golf gloves may be used when batting. Game play, however, is very different.

The name "over-the-line" is a registered trademark of the Old Mission Beach Athletic Club (OMBAC) of San Diego, California, which organizes an annual tournament that is one of the city's largest summer social events. It is also known as OTL (also trademarked by OMBAC). OMBAC allows other organizations to license the trademark for their own events for a nominal fee.

An over-the-line court is normally made up on a beach and comprises a triangle and an open ended rectangle marked by ropes or lines in the sand. The base ("The Line") of the triangle is 55 feet (17 m) long, and the distance from the line to the opposite point ("Home") is also 55 feet (17 m). The rectangle is composed of two parallel ropes or lines that extend out indefinitely away from home starting from the two ends of The Line and at a right angle to The Line. The area between the parallel ropes and over The Line is fair territory. Everything other than the triangle and fair territory is foul territory.