The Lancers is a dance for 8 or 16 pairs, thought to date from 1820 and originally known as 'the quadrille of the Lancers'. It is also the name of the music for this dance.
Lancers were cavalrymen who fought with lances (long weapons with wooden shafts and steel tips). Some cavalry regiments of the British army have retained the word Lancers in their titles.
Listen on Spotify to Lancier-Quadrille No. 4 by Anton Bruckner.