Dance in art - Degas' 'The Little Fourteen-Year-Old Dancer'

The model for Degas' 'The Little Fourteen-Year-Old Dancer' ('La Petite Danseuse de Quatorze Ans'), modeled in 1880, was Marie Van Goethem, a student at the École de Danse in Paris and dancer at the Opéra. The sculpture received mixed reviews at the time it was first displayed (it was cast in 1922) as some reviewers thought it appallingly ugly. I think she's wonderfully life-like (especially since she's life-size!).

Degas seems to have captured her during a moment of contemplation perhaps while being shown a new step or simply while "standing at the side of the classroom, perhaps admiring older, more advanced dancers in an exercise" as Evan @ DancingPerfectlyFree suggested.

Lovely:

Dance in art - Bruegel's 'The Peasant Dance'

Pieter Bruegel the Elder was a Renaissance painter from the Netherlands who is known for his paintings of peasants and landscapes. In 'The Peasant Dance', painted in 1568, we see a jolly group of ordinary folk enjoying a real 'knees-up' (as the Brits would say)! The beer's a-flowin', there's a piper playing some (no doubt) lively tunes, and we can see three couples kicking their heels up to the music.

Now that's what I call a party!