Bryennios or Bryennius (Greek: Βρυέννιος), feminine form Bryennissa (Βρυέννισσα), was the name of a noble Byzantine family which rose to prominence in the 11th and 12th centuries, mostly as military commanders. The etymology of the name is uncertain. The first members of the family appear in the 9th century. None are known for the 10th, but they reappear in the latter half of the 11th century, when they rose to high military commands and became associated with the Komnenian dynasty. Members of the family retained high positions through the 12th century, and are documented up to the 15th century.
- Alexios Bryennios, megas doux in 1156
- Joseph Bryennios (ca. 1350 – 1430), Byzantine monk and writer
- Manuel Bryennios (fl. 1300), Byzantine scholar
- Nikephoros Bryennios (ethnarch) (fl. 1050s), Byzantine general
- Nikephoros Bryennios the Elder (fl. 1070s), Byzantine general, son of the ethnarch, who made an attempt on the throne of Michael VII Doukas in 1077-1078
- Nikephoros Bryennios the Younger (1062–1137), son or grandson of the preceding, Byzantine general, statesman and historian, husband of Anna Komnene