Omega SA is a Swiss luxury watchmaker based in Biel/Bienne, Switzerland. Founded by Louis Brandt in La Chaux-de-Fonds in 1848, the company formerly operated as Louis Brandt et Fils until incorporating the name Omega in 1903, becoming Louis Brandt et Frère-Omega Watch & Co. In 1984, the company officially changed its name to Omega SA and opened its museum in Biel/Bienne to the public. Omega is a subsidiary of the Swatch Group.

Britain's Royal Flying Corps used Omega watches in 1917 for its combat units, followed by the U.S. Army in 1918, and NASA in 1969 for Apollo 11. The Omega Speedmaster Moonwatch is marketed as the first watch worn on the Moon, becoming one of the watchmaker's most iconic models.

Omega is the current official timekeeper of the Olympics, having first done so in 1932, in addition to being the timekeeper of the America's Cup yacht race.

In 1848, Louis Brandt founded the company that would become Omega in La Chaux-de-Fonds, Switzerland. He assembled key-wound precision pocket watches from parts supplied by local craftsmen. He sold his watches from Italy to Scandinavia by way of England, his chief market. In 1877, his sons Louis-Paul and César joined him, and the company name was changed to Louis Brandt & Fils. In 1894, his two sons Louis-Paul and César developed their own in-house manufacturing and total production control system that allowed component parts to be interchangeable. Watches developed with these techniques were marketed under the Omega brand of Louis Brandt & Frere. By 1903, the success of the Omega brand led Louis Brandt & Frere to rename their company to the Omega Watch Co.

Louis-Paul and César Brandt both died in 1903, leaving one of Switzerland's largest watch companies — with 240,000 watches produced annually and employing 800 people — in the hands of four young people, the oldest of whom, Paul-Emile Brandt, was not yet 24. The economic difficulties brought on by the First World War led Paul-Emile Brandt to work in 1925 towards the union of Omega and Tissot, then to their merger in 1930 into the group SSIH, Geneva.

Under Brandt's leadership and Joseph Reiser's from 1955, the SSIH Group continued to grow and multiply, absorbing or creating some fifty companies, including Lanco and Lemania, manufacturer of the most famous Omega chronograph movements. By the 1970s, SSIH had become Switzerland's top producer of finished watches and third in the world. Up to this time, Omega outsold Rolex, its main Swiss rival in the luxury watch segment, in the race for "King of Swiss Watch brands", although Rolex sold at a higher price point. Omega tended to be more revolutionary and more professionally focused, while Rolex watches were more ‘evolutionary’ and famous for their mechanical pieces and branding.

While Omega and Rolex had dominated in the pre-quartz era, this changed in the 1970s during the quartz crisis, when Japanese watch manufacturers, such as Seiko and Citizen, rose to dominance due to their use of quartz movements. In response, Rolex continued concentrating on its expensive mechanical chronometers where its expertise lay (though it did have some experimentation in quartz), while Omega tried to compete in the quartz watch market with its own quartz movements.

Weakened by the severe monetary crisis and recession of 1975 to 1980, SSIH was bailed out by banks in 1981. During this period, Seiko expressed interest in acquiring Omega, but nothing came of the talks.