The place was first documented in 1071, as "Lohes". The name has changed considerably over the years: Lothae, Lo, Lohes, Loes, Loez and Loos. It was not until 1791 that the name of "Loos" was officially sanctioned. According to some, the name comes from the Germanic "Lôh" and Dutch "Loo" which mean "wood", but there is no archaeological evidence of what could have been a forest. According to others, the name derives from the Germanic "Laupo" which means marshy meadows, which, given the topography of the town, tends to support this theory. In 1937, after much confusion with Loos-lez-Lille (today Loos), it was decided to add the region’s name (Gohelle) to that of the commune.
The oldest documents that specify the existence of Loos date from the eleventh century, at the time of construction of the abbey of Anchin. But with the foundation of a church dedicated to Saint Vaast, it suggests that the village existed long before (St. Vaast lived in the 6th century).
It was around 1850 that the town started to become prosperous; farmers could fertilize previously uncultivated land, thanks to technology provided by Guislain Decrombecque and the discovery of coal resulted in a very rapid increase of population. Many monuments and cemeteries reflect the destruction during World War I which completely destroyed the town, particularly during the Battle of Loos, from 25 September - 8 October 1915. At the end of the war, not a single building or tree had survived the pounding of artillery. Reminders of the war persist with the periodic discovery of unexploded ordnance.
The mining infrastructure, industry and transport were hit again during World War II.
Coal was mined here from 1855 until 1986. The very rural village changed into a town, with many foreign workers, especially from Poland, swelling the workforce. A former mining site (Écopole) has been preserved and now hosts many cultural, economic and environmental activities which are the symbol of new developments for the commune. Écopole 11/19 comprises buildings dating from 1923 and a modern concrete winding tower (height 66m) which operated from 1960 to 1986.
The landscape is still marked by enormous spoil heaps, those of pits 11 and 19, visible for miles around. They are part of the mines of the Nord-Pas de Calais region that have become the 38th French site on the list of UNESCO World Heritage Sites as "a living and changing landscape".