Sony的Betamax，简称Beta是一种年份较早的专业用 19.1毫米（0.75英寸） U-matic录像带演进而来的 12.7毫米（0.50英寸） 家用录像带格式。它于1975年4月16日发表，同年5月10日上市。如同1976年JVC公司发表的VHS制式，它没有guard band，使用水平录制以减少漏话。Betamax名字的由来有两种说法。一种是当磁带在机器中运转时，它环绕机件的样子像希腊字母"Beta"。另一种说法是"Beta"在日文中是"品质"的意思，而"max"则用来形容"beta"。

Betamax (also called Beta, and referred to as such in the logo) is a consumer-level analog videocassette magnetic tape recording format developed by Sony, released in Japan on May 10, 1975. The first Betamax introduced in America was the LV-1901 console, which included a 19" color monitor, and appeared in stores in early November, 1975. The cassettes contain .50 in (12.7 mm)-wide videotape in a design similar to the earlier, professional .75 in (19 mm) wide, U-matic format. The format is obsolete, having lost the videotape format war to VHS. Betamax recorders ceased production in 2002, but the format's cassette tapes were available until March 2016, when Sony discontinued them.