He was an Arian Christian barbarian and was the son of a prince of the Suebi and the daughter of Wallia, king of the Visigoths. His youth was spent at the court of the western Roman emperor Valentinian III, where he won distinction fighting under Aetius, Valentinian's magister militum of the western portion of the Roman Empire.
The deaths of Valentinian and Aetius in 454-55 created a power vacuum in the west. At first Petronius Maximus attempted to seize control of the imperial throne, but he was killed when the Vandal king Geiseric sacked Rome in May of 455. Avitus was then made Emperor by the Visigoths, and following his arrival in Rome, Avitus appointed Ricimer as commander of the strickened Western Empire (by then reduced to Italy and a part of southern Gaul) and raised a new army and navy from among the German mercenaries available to him.
After leaving Rome, Geiseric had left a powerful fleet essentially blockading the Italian coast. Ricimer led his own fleet out to sea, and in 456, defeated the Vandals in a sea-fight near Corsica, and on land near Agrigentum in Sicily. Backed by the popularity thus acquired, Ricimer then gained the consent of the Roman Senate to an expedition against the emperor Avitus, whom he defeated in a bloody battle at Piacenza on October 16, 456. Avitus was taken prisoner and made bishop of Piacenza, and shortly afterwards sentenced to death. Ricimer then obtained from Leo I, the eastern emperor at Constantinople, the title of Patrician.
Ricimer spent the rest of his life as the de facto ruler of what was left of the western empire. However, the way in which he exercised power made him one of the most controversial figures of his time. As a German, he could not assume the title of Augustus (emperor) himself; on the other hand, power over the Augustus in Rome gave him prestige and offered him some influence over the other Germanic peoples occupying Gaul, Hispania, and Northern Africa. This left him with two options - dissolve the western imperial court and rule officially as a dux, or governor, of a single emperor in Constantinople, or set up his own figurehead emperors and rule through them. He chose to do the latter, even going so far as to have his name inscribed on the coinage along with the emperor.
In 457, Ricimer set up Majorian as his own emperor in the West and induced Leo to give his consent. However, Majorian proved to be a capable ruler and soon became uncomfortably independent. Majorian was defeated (possibly by treachery) by Geiseric near the modern city of Valencia, Spain, while trying to organize an expedition against him, in 461. Ricimer then forced him to abdicate and caused his assassination on August 7, 461. The successor whom Ricimer placed upon the throne was Libius Severus, who proved to be more docile than Majorian, but had to face the disapproval of Leo in the East and rivalry of Aegidius in Gaul. Upon Libius Severus' death in 465 - said to be due to the poison of Ricimer - this emperor-maker ruled the West for eighteen months without an emperor.
Finally, after a lengthy debate in which he and Geiseric, now working together, tried to force upon Leo their own candidate as emperor, Ricimer accepted Leo's candidate Anthemius. He diplomatically married Anthemius' daughter, and for some time lived in peace with him.
Ricimer commanded a large portion of the Roman forces in an expedition mounted by Leo against Geiseric in 468. His behavior was more than a little suspect and raised suspicions that Ricimer secretly wanted the expedition to fail, which it ultimately did.
Four years later, Ricimer moved to Mediolanum (Milan), ready to declare war upon Anthemius. St. Epiphanius, bishop of Milan, patched up a short-lived truce, after which Ricimer was again before Rome with an army of Germans. He proclaimed as emperor Olybrius, the candidate for emperor he and Geiseric had once favored, and after three months' siege took the city, on July 1, 472. Anthemius was killed and Rome was a prey to Ricimer's soldiers. He himself, however, died less than two months later of malignant fever. His title of Patrician was assumed by his nephew Gundobad.