Princess Leia Organa (later Leia Organa Solo) was the daughter of Anakin Skywalker (Darth Vader) and Padmé Amidala. Her character has gone through many stages in the Star Wars films and Expanded Universe. In the movies, she is a senator and leader of the Rebel Alliance. In the novels and comics that follow, she is a leader in the New Republic, serving several terms as Chief of State. Many years later, she sets aside her political career to become a Jedi Knight, just like her father, brother, and children.
Princess Leia in the Star Wars Films
Episode III: Revenge of the Sith
Princess Leia was born Leia Amidala Skywalker on Polis Massa in 19 BBY. After the death of their mother, Padmé Amidala, in childbirth, Leia and her twin brother Luke were separated. Obi-Wan Kenobi brought Luke to Tatooine to live with his aunt and uncle, Owen and Beru Lars, while Leia was adopted by Bail Organa, senator and Prince Consort of Alderaan, and his wife, Queen Breha.
Episode IV: A New Hope
At 18, Leia became the youngest Imperial Senator ever elected. As a member of the Rebel Alliance, she used her diplomatic immunity and Senate ships to run secret supply missions. One of these missions -- an attempt to contact General Obi-Wan Kenobi -- ended with her capture by Darth Vader, who at that time was unaware of Leia's identity. Obi-Wan helped Luke Skywalker and Han Solo rescue Leia, but died in the process. The plans that Leia had helped recover -- and hidden within the droid R2-D2 -- allowed the Rebels to successfully destroy the Death Star at Yavin soon after.
Episode V: The Empire Strikes Back and Episode VI: Return of the Jedi
Leia began to develop a romance with fellow Rebel and smuggler Han Solo after they escaped the ice planet Hoth together. Before Han was frozen in carbonite, she confessed, "I love you," to which Han only replied, "I know." Months passed before she was able to rescue Han from the crime lord Jabba the Hutt. Leia freed Han while disguised as the bounty hunter Boushh, but was herself captured. She later avenged herself by strangling Jabba to death with her own chain.
At the Battle of Endor, Leia was part of Han Solo's strike team, sent to the forest moon to disable the second Death Star's energy shield. After getting separated from the group, she encountered a tribe of Ewoks, small, bear-like aliens, who later became the Rebels' allies and helped bring down the shield. Before Luke Skywalker left the forest moon to confront Darth Vader, he told Leia the truth about their parentage.
Princess Leia after Return of the Jedi
After defeating the Empire at the Battle of Endor, the Rebels went on to found a New Republic. Leia served as Minister of State and later succeeded Mon Mothma as Chief of State. She served for six (non-concurrent) years, with her final term ending before the Yuuzhan Vong invasion. As Chief of State, she would lead the New Republic through a number of political crises, and after she left politics she continued to fight for the New Republic (and later the Galactic Alliance).
After a tumultuous courtship, Leia married Han Solo in 8 ABY (eight years after the Battle of Yavin in A New Hope). They had three children -- Jaina, Jacen, and Anakin -- who would all become powerful Jedi. Tragically, she felt two of her children die young, one during the Yuuzhan Vong War and another during the Second Galactic Civil War. She and Han then helped raise their young grandchild.
Like her twin brother, Leia was Force-sensitive; however, her role as a politician and leader of the New Republic prevented her from devoting too much time to Jedi training. Luke taught her basic lightsaber defense and Force techniques, but it was not until nearly 40 ABY, years after she had left the political realm, that Leia became a fully-fledged Jedi Knight.