SOS was ABBA's third single from the 1975 album ABBA. It was released with Man in the Middle as the B-side. Agnetha Fältskog, who was the lead vocalist, also recorded the song in Swedish for her 1975 album Elva kvinnor i ett hus. SOS was ABBA's first major worldwide hit since Waterloo the year before.
The promotional video released alongside the single was directed by Lasse Hallström. It was recorded over two days alongside the videos for Mamma Mia, I Do, I Do, I Do, I Do, I Do and Bang-A-Boomerang for 50,000 Swedish krona. Adjusted for inflation up to 2021, this is equivalent to approximately 290,000 Swedish krona, or £24,000. The music video was uploaded to YouTube on October 8 2009, and on August 13 2021 it was reported that the video was available in 4K for the first time. As of August 2021, the video has over 64 million views on YouTube.