Alfredo Yu is a fictional character in the Honorverse, a series of military science fiction novels written by David Weber.

A native of the People's Republic of Haven, Alfredo Yu first appeared as an officer in the Havenite Navy in the series' second novel, The Honor of the Queen. Unlike many of the senior officers of the People's Navy, Yu had risen to the rank of Captain by his own merits, as he was not a member of the Legislaturalists (thus lacking the patronage and favoritism available to them), becoming the commanding officer of the battlecruiser PNS Saladin. He was, however, an atypical Havenite naval officer, and he was almost expelled from the Havenite naval academy for possessing history books which dated from before the formation of the People's Republic.

Saladin was "transferred" to the Masadan Navy together with the destroyer PNS Breslau (commanded by another highly capable Havenite officer, Thomas Theisman), as part of a deal between Haven and Masada. Captain Yu was "loaned" to the Masadans in order to train them in the use of such modern warships, and was given a commission in the Masadan Navy as commanding officer of Thunder of God, as the Saladin was renamed.

During Masada's brief war with Grayson, Yu helped the Masadan Navy in devastating Grayson's smaller fleet, but soon became appalled by the Masadans' cruelty and incompetence. Distrusted by the Masadans, Yu and the rest of the Havenite officers were forced to abandon Thunder of God as the Masadans sent an assault force to seize control of her. After Thunder of God's destruction by Honor Harrington and Masada's conquest by the Manticorans, Yu and his surviving officers defected to Manticore. They were thoroughly interrogated about the People's Navy and its capabilities.

Alfredo Yu was later sent to Grayson where (in an ironic twist of events) he trained the navy he once almost destroyed into modern warfare tactics and technology. He later became a citizen of Grayson and was given a commission in the Grayson Navy as captain of the superdreadnought GNS Terrible, a former Havenite warship captured by the Manticorans. As Terrible's commanding officer, he also served as Honor Harrington's flag captain during the Fourth Battle of Yeltsin. In Grayson, Yu decided to cut all ties with the People's Republic.

He continued his career in the Grayson Navy, reaching the rank of Admiral and being appointed as the second-in-command (and de facto commander) of the Protector's Own Squadron, a force which includes many Havenite defectors and former prisoners-of-war of the People's Republic.