A sweater vest, also known as a sleeveless sweater and tank top (UK), is an item of knitwear that is similar to a sweater, but without sleeves. They were popular in the 20th century, particularly in the 1970s in the UK, and are again growing in popularity in this century.

The name "tank top", recorded in English since 1968, derives from its resemblance to a tank suit, a style of one-piece women's swimsuit with shoulder straps, so called since the 1920s, because it was worn in a "swimming tank", an obsolete term for a swimming pool. In American English, a tank top refers to a sleeveless shirt.

One of the most common patterns on a sleeveless sweater is argyle. Many newer designs feature a return to popular patterns from eras past. Other variations include designs of a more modern nature, including stripes. Some of the most common of neckline shapes are the V-neck and the crew neck, which is similar to a common T-shirt neckline.

Sleeveless sweaters are popular among sports fans, especially those who play golf. Those with sports team logos, especially NFL and college teams, are also popular and are frequently seen being worn by American football coaches, most notably Jim Tressel who has been given the nickname "The Sweater Vest" by many American football fans despite the garment's origins at rival Michigan.