Esther was the wife of King Xerxes who ruled over 127 provinces stretching from India to Cush and heroine of the book that bears her name.
She was a Jewess named Hadassah, born to Abihail of the tribe of Benjamin. Her family didn't avail of the permission granted by Cyrus to the exiles to return to Jerusalem, preferring to remain in Persia. She stayed with her cousin Mordecai who worked in the household of the Persian king.
Soon after a drunk King Xerxes divorced his wife Vashti, because she chose not to obey his instructions to "display her beauty to the people and nobles", he chose Esther to be his wife, selecting her from hundreds of women in the nation.
Now the king was attracted to Esther more than to any of the other women, and she won his favor and approval more than any of the other virgins. So he set a royal crown on her head and made her queen instead of Vashti. (Esther 2:17)
The selection was undoubtedly inspired by God who would use her to save a nation. She did this when Haman, the prime minister of Persia, managed to get the authority to kill all the Jews throughout the Persian empire. Esther helped stop this terrible catastrophe from taking place, and Hanan, the master mind of the insiduous plan found himself on the gallows he had built for Mordecai, a man he detested.
The Jews established an annual feast known as the feast of Purim to commemorate this deliverance.