Anna Komnene (Greek: Ἄννα Κομνηνή, romanized: Ánna Komnēnḗ; 1 December 1083 – 1153), commonly Latinized as Anna Comnena, was a Byzantine Greek historian. She is the author of the Alexiad, an account of the reign of her father, Byzantine emperor Alexios I Komnenos. Her work constitutes the most important primary source of Byzantine history of the late 11th and early 12th centuries, as well as of the early Crusades. Although she is best known as the author of the Alexiad, Anna played an important part in the politics of the time and attempted to depose her brother John II Komnenos as emperor in favour of her husband, Nikephoros Bryennios the Younger.

At birth, Anna was betrothed to Constantine Doukas, and she grew up in his mother's household. She was well-educated in "Greek literature and history, philosophy, theology, mathematics, and medicine." Anna and Constantine were next in the line to throne until Anna's younger brother, John II Komnenos, became the heir in 1092. Constantine died around 1094, and Anna married Nikephoros Bryennios in 1097. The two had several children before Nikephoros' death around 1136.

It is commonly believed that, following her father's death in 1118, Anna and her mother attempted to usurp John II Komnenos. Supposedly her husband refused to cooperate with them, and the usurpation failed. As a result, John exiled Anna to the Kecharitomene Monastery, where she spent the rest of her life, and in her confinement there she wrote the Alexiad. However, there is no contemporary evidence of Anna's involvement in any assassination attempt.

Anna was born on 1 December 1083 to Alexios I Komnenos and Irene Doukaina. Her father, Alexios I Komnenos, became emperor in 1081, after usurping the previous Byzantine Emperor, Nikephoros Botaneiates. Her mother, Irene Doukaina, was part of the imperial Doukas family. In the Alexiad, Anna emphasises her affection for her parents in stating her relationship to Alexios and Irene. She was the eldest of seven children; her younger siblings were (in order) Maria, John II, Andronikos, Isaac, Eudokia, and Theodora.

Anna was born in the Porphyra Chamber of the imperial palace in Constantinople, making her a porphyrogenita, which underscored her imperial status. She noted this status in the Alexiad, stating that she was "born and bred in the purple." According to Anna's description in the Alexiad, her mother asked Anna to wait to be born until her father returned from war. Obediently, Anna waited until her father came home.

At birth, Anna was betrothed to Constantine Doukas, the son of Emperor Michael VII and Maria of Alania. The two were the heirs to the empire until sometime between c.1088 and 1092, after the birth of Anna's brother, John II Komnenos. Various scholars point out that the betrothal was probably a political match intended to establish the legitimacy of Anna's father, who had usurped the previous emperor.

Starting around 1090, Constantine's mother – Maria of Alania – raised Anna in her home. It was common in Byzantium for mothers-in-law to raise daughters-in-law. In 1094, Maria of Alania was implicated in an attempt to overthrow Alexios I Komnenos. Some scholars argue that Anna's betrothal to Constantine Doukas may not have ended there, as he was not implicated in the plot against Alexios, but it certainly ended when he died around 1094.

Anna's relationships to her mother-in-law Maria of Alania, her paternal grandmother Anna Dalassene, and her mother Irene Doukaina, have been noted as sources of inspiration and admiration for Anna. For example, Thalia Gouma-Peterson argues that Irene Doukaina's "maternal ability to deal with the speculative and the intellectual enables the daughter to become the highly accomplished scholar she proudly claims to be in the opening pages of the Alexiad."