The Times Square Ball is a time ball located in New York City's Times Square. Located on the roof of One Times Square, the ball is a prominent part of a New Year's Eve celebration in Times Square commonly referred to as the ball drop, where the ball descends down a specially designed flagpole, beginning at 11:59:00 p.m. ET, and resting at midnight to signal the start of the new year. In recent years, the ball drop has been preceded by live entertainment, including performances by musicians.

The event was first organized by Adolph Ochs, owner of The New York Times newspaper, as a successor to a series of New Year's Eve fireworks displays he held at the building to promote its status as the new headquarters of the Times, while the ball itself was designed by Artkraft Strauss. First held on December 31, 1907, to welcome 1908, the ball drop has been held annually since, except in 1942 and 1943 in observance of wartime blackouts.

The ball's design has been updated four times to reflect improvements in lighting technology; the original ball was 5 feet (1.5 m) in diameter, constructed from wood and iron, and illuminated with 100 incandescent light bulbs. By contrast, the current ball is 12 feet (3.7 m) in diameter, and uses over 32,000 LED lamps. Since 1999–2000, the ball has featured an outer surface consisting of triangular panels manufactured by Waterford Crystal, which contain inscriptions representing a yearly theme.

The event is organized by the Times Square Alliance and Countdown Entertainment, a company led by Jeff Strauss. Since 2009, the ball has been displayed atop One Times Square nearly year-round, while the original, smaller version of the current ball that was used in 2008 has been on display inside the Times Square visitor's center. The prevalence of the Times Square ball drop has inspired similar "drops" at other local New Year's Eve events across the country; while some use balls, some instead drop objects that represent local culture or history.