Nikephoros Melissenos (Greek: Νικηφόρος Μελισσηνός, c. 1045 – 17 November 1104), Latinized as Nicephorus Melissenus, was a Byzantine general and aristocrat. Of distinguished lineage, he served as a governor and general in the Balkans and Asia Minor in the 1060s. In the turbulent period after the Battle of Manzikert in 1071, when several generals tried to seize the throne for themselves, Melissenos remained loyal to Michael VII Doukas and was exiled by his successor Nikephoros III Botaneiates. In 1080–1081, with Turkish aid, he seized control of what remained of Byzantine Asia Minor and proclaimed himself emperor against Botaneiates. After the revolt of his brother-in-law Alexios I Komnenos, however, which succeeded in taking Constantinople, he submitted to him, accepting the rank of Caesar and the governance of Thessalonica. He remained loyal to Alexios thereafter, participating in most Byzantine campaigns of the period 1081–1095 in the Balkans at the emperor's side. He died on 17 November 1104.

Nikephoros Melissenos was probably born c. 1045 at Dorylaeum, where his family had extensive estates. Through both his father and his mother, he was of aristocratic descent: his father belonged to the Bourtzes line, while his mother to the illustrious Melissenos family, which dated back to the 8th century and had produced several distinguished generals.

Sometime before 1067, Nikephoros married Eudokia Komnene. Born c. 1052, she was the second daughter of the Domestic of the Schools John Komnenos and Anna Dalassene and sister of the future Byzantine emperor Alexios I Komnenos (r. 1081–1118). They had at least one known son, the parakoimomenos John Komnenos.

By 1067, Melissenos held the rank of magistros and the post of military governor (doux) in Triaditza (modern Sofia). In 1070, he joined the field army commanded by his eldest brother-in-law, Manuel Komnenos, in a campaign against the Seljuk Turks. The campaign ended in defeat near Sebasteia (modern Sivas), and Melissenos along with Manuel Komnenos were captured by a Turkish chieftain whom the Byzantines called Chrysoskoulos. Manuel, however, quickly persuaded the Turk to enter into Byzantine service, and their captivity ended.

Melissenos remained loyal to Michael VII Doukas (r. 1071–1078) during the rebellion of the strategos of the Anatolic Theme, Nikephoros Botaneiates (Nikephoros III), which began in October 1077. Michael VII rewarded him by appointing him to Botaneiates's post, but after Botaneiates's victory and entry into Constantinople in April 1078, Melissenos was exiled to the island of Kos.

In autumn 1080, Melissenos left Kos and returned to Asia Minor. There, he succeeded in gaining the support of the local population, and in recruiting many Turkish tribesmen as mercenaries to his army. One by one, the cities of western and central Asia Minor opened up their gates to him, and Turkish garrisons were installed in them. Botaneiates tried to send Alexios Komnenos, who had recently suppressed the revolts of Nikephoros Bryennios and Nikephoros Basilakes, against him, but he refused. In February 1081, Melissenos's troops took Nicaea, where he was acclaimed as emperor. A loyalist army under the eunuch protovestiarios John, George Palaiologos and Kourtikes was sent against him, but was defeated almost without battle, and withdrew to the capital.

In March 1081, Melissenos was encamped with his army at Damalis, on the Asian shore across the Bosporus from Constantinople. There, he received news of the revolt of the Komnenoi against Botaneiates and the proclamation of Alexios Komnenos as emperor. He sent letters to the Komnenoi, suggesting a division of authority over the imperial territory, with the Balkans remaining under Komnenian control and himself keeping Asia Minor, although he also emphasized that the Byzantine Empire should remain formally united. In reply, the Komnenoi offered to recognize him as Caesar – the second highest dignity after the imperial title itself – and to give him the governance of Thessalonica – the Empire's second-most important city – if he would submit to them. Melissenos initially refused to accept this offer, but as the Komnenoi were on the verge of taking Constantinople and might refuse to make similar concessions later, he eventually agreed.

At the same time, Nikephoros Botaneiates tried to forestall the capital's fall to the Komnenoi by sending for Melissenos and asking him to enter the city and assume imperial authority. His envoys, however, were obstructed by George Palaiologos and never reached Melissenos. Thus Constantinople fell to the Komnenian forces, and on 8 April 1081, Melissenos too entered the imperial capital. True to his word, Alexios I raised him to Caesar and gave him authority over Thessalonica, as well as allotting the city's revenues to his income. At the same time, however, Alexios raised his brother Isaac Komnenos to the newly created dignity of sebastokrator, which he placed above that of Caesar, bypassing Melissenos.