When she was born in 1926 no-one expected Princess Elizabeth to become Queen.
Her father George was not the King and he didn't think he ever would be.
George had an older brother called Edward. Because Edward was the eldest son he would get to be King.
Things changed when Edward fell in love with an American woman. She had already been married and divorced. Because of this she could never be Queen.
Edward gave up the throne so he could marry the woman he loved.
The Queen and her father
Princess Elizabeth's father took over the job and became King George VI.
King George led the country through the second world war but in 1952 he died of lung cancer.
Princess Elizabeth was his eldest child. She became Queen Elizabeth II.