The Theme of Mylasa and Melanoudion (Greek: θέμα Μυλά[σ]σης και Μελανουδίου) was a Byzantine province (thema) in southwestern Asia Minor (modern Turkey) in the 12th and 13th centuries.
It is first attested in 1127/1128, and was probably created sometime after 1110, either by Alexios I Komnenos (r. 1081–1118) or by his son and successor John II Komnenos (r. 1118–1143), out of territory regained from the Seljuk Turks during the 1090s. Originally named simply the Theme of Mylasa, it was renamed after its seat moved from Mylasa (modern Milas) to the town of Melanoudion – as yet not conclusively identified, it lay south of Miletus – sometime in ca. 1150–1175.