Oxygen (foaled 1828, died in winter 1854–1855) was a British Thoroughbred racehorse and broodmare who won the classic Oaks Stakes at Epsom Downs Racecourse in 1831.

Apart from Oxygen, Emilius’s best winners included Priam, Plenipotentiary, Riddlesworth (2000 Guineas) and Mango (St Leger) and he was British Champion sire in 1830 and 1831.

[1] Oxygen's dam, Whizgig was a daughter of the Duke of Grafton's outstanding broodmare Penelope, making her a half-sister to Derby winners Whalebone and Whisker.

[4] Oxygen made her debut in this race on 12 July 1830 and finished second of the eight runners, two lengths behind a colt named Zany, with the future Derby winner Spaniel among the unplaced horses.

Ridden by John Barham Day, Oxygen won the five furlong race impressively by two or three lengths from Lord Egremont's unnamed black filly.

After her win in the Clearwell Stakes Oxygen was made favourite for the following year's Oaks ahead of the Yorkshire-trained Circassian, with the two fillies dominating the betting markets.

She failed to emulate her dam as she finished third (officially "unplaced") behind the upset winner Galantine after an extremely slow early pace resulted in the race developing into sprint over the last furlong.

Ridden as usual by Day, Oxygen overtook the front-running Delight in the straight and won by a neck[13] from Lord Exeter's filly Marmora, with Guitar third and the favourite Circassian in fourth.

Carrying a weight of 107 pounds and ridden by Patrick Conolly, she started the 2/1 favourite and demonstrated a "game heart"[19] to win by a length from the colts Mazeppa and Sarpedon.

[1] At the next meeting Oxygen contested a 100 guinea King's Plate over the three and a half mile Round Course against the 1830 Ascot Gold Cup winner Lucetta, from whom she was receiving twenty pounds.