Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 frames) per second, and associated with CCIR analogue broadcast television systems B, D, G, H, I or K. The articles on analog broadcast television systems further describe frame rates, image resolution, and audio modulation.

PAL video is composite video because luminance (luma, monochrome image) and chrominance (chroma, colour applied to the monochrome image) are transmitted together as one signal. A latter evolution of the standard, PALplus, added support for widescreen broadcasts with no loss of vertical image resolution, while retaining compatibility with existing sets. Almost all of the countries using PAL are currently in the process of conversion, or have already converted transmission standards to DVB, ISDB or DTMB. The PAL designation continues to be used in some non-broadcast contexts, especially regarding console video games where it is referring to the markets other than North America and Japan.

PAL was adopted by most European countries, by several African countries, including South Africa, by Argentina, Brazil, Paraguay, Uruguay, and by most of Asia Pacific (including the Middle East and South Asia). Countries in those regions that did not adopt PAL were France, Francophone Africa, several ex-Soviet states, Japan, South Korea, Liberia, Myanmar, the Philippines, and Taiwan.

With the introduction of home video releases and later digital sources (e.g. DVD-Video), the name "PAL" might be used to refer to digital formats, even though they use completely different colour encoding systems. For instance, 576i (576 interlaced lines) digital video with colour encoded as YCbCr, intended to be backward compatible and easily displayed on legacy PAL devices, is usually mentioned as "PAL" (eg: "PAL DVD"). Likewise, video game consoles outputting a 50 Hz signal might be labeled as "PAL", as opposed to 60 Hz on NTSC machines. These designations should not be confused with the analog colour system itself.

In the 1950s, Western European countries began plans to introduce colour television and were faced with the fact that the NTSC standard demonstrated several weaknesses, including colour tone shifting under poor transmission conditions, which became a major issue considering Europe's geographical and weather-related particularities. To overcome NTSC's shortcomings, alternative standards were devised, resulting in the development of the PAL and SECAM standards. The goal was to provide a colour TV standard for the European picture frequency of 50 fields per second (50 hertz), and finding a way to eliminate the problems with NTSC.

PAL was developed by Walter Bruch at Telefunken in Hanover, West Germany, with important input from Gerhard Mahler [de]. The format was patented by Telefunken in December 1962, citing Bruch as inventor, and unveiled to members of the European Broadcasting Union (EBU) on 3 January 1963. When asked why the system was named "PAL" and not "Bruch", the inventor answered that a "Bruch system" would probably not have sold very well ("Bruch" is the German word for "breakage").

The first broadcasts began in the United Kingdom in July 1967, followed by West Germany at the Berlin IFA on August 25. The BBC channel initially using the broadcast standard was BBC2, which had been the first UK TV service to introduce "625-lines" during 1964. The Netherlands and Switzerland started PAL broadcasts by 1968, with Austria following the next year.

Telefunken PALcolour 708T was the first PAL commercial TV set. It was followed by Loewe-Farbfernseher S 920 and F 900.