SubStation Alpha (SSA) is a text-based subtitle format used for creating and displaying subtitles with advanced formatting options, such as different fonts, colors, sizes, and positioning. It is popular in the fansubbing community for anime and other media and is compatible with various subtitle editors and media players.

SubStation Alpha was created by CS Low, also known as Kotus, in 1996 for the anime fansubbing community. The format allowed for advanced text styling and positioning, which were crucial for creating visually rich subtitles. SSA quickly gained popularity due to its robust features and ease of use. It supports various text effects, including different fonts, colors, and karaoke effects. While the Advanced SubStation Alpha (ASS) format later introduced additional features, SSA remains widely used and supported by many media players and subtitle editors.