Iphigenia was the daughter of King Agamemnon and his queen Clytemnestra. When they were on their way to the Trojan War the fleet was becalmed in Aulis. The prophet Calchas said that the goddess Artemis demanded her as a sacrifice. Agamemnon brought her to the spot on the pretext that she was to be married to Achilles. This is the subject of the Euripides play Iphigenia in Aulis.
The cowardice of Agamemnon in the face of pleading by Clytemnestra and Achilles, once they know what is going, are part of the reason why when Agamemnon was off at the war, she took a lover Aegisthus, and they killed Agamemnon on his return; and their son Orestes and other daughter Electra vowed revenge on her, plugging into the whole Orestes-Electra vengeance cycle.
A different part of the legend says that Artemis then substituted a deer for her at the last moment and took her off to the land of the savage Tauri in the Chersonese (now Crimea), where she served as the goddess's priestess. These people had a cruel custom of sacrificing strangers who landed on their shore. Orestes and his faithful friend Pylades arrived, but she recognized him and they all escaped, carrying spoils from the temple. This story is told in Euripides' play Iphigenia in Tauris.
Her name means 'strongly or powerfully born': the first element is apparently related to the Latin vis, vim. The Greek is actually Iphigeneia so it should strictly have stress on the final I. Her name is sometimes given as Iphianassa.
The Euripides stories were used by Jean Racine in his play Iphigénie and by Christoph Willibald Gluck in his baroque operas Iphigénie en Aulide and Iphigénie en Tauride.