|King of Trellin and Emperor of Hysera|
|Reign||23 September-29 October 1047|
|Born||16 February 988|
|Died||4 September 1056 (aged 68)|
Pethmil IV (16 February 988 - 4 September 1056), also known as Pethmil of Rosnai, was King of Trellin for five weeks in 1047. He was proclaimed king after a quick succession of rulers in the Year of Five Kings .
Pethmil was one of a number of generals who rebelled against Jemeg I, the brother-in-law of King Mokhra II who had been deposed by Palav ti'Eza. The commander of the garrison town of Rosnai, he led an army to Mar'theqa and captured King Jemeg, who had attempted to buy him off. After putting Jemeg to death Pethmil was crowned king, but he learned soon after that another general, Tarmüz Falaan, was leading an army to depose him. Tarmüz had originally claimed the throne for himself but marched on Mar'theqa in the name of King Jemeg. Pethmil recognised his imminent fate and offered to abdicate. Tarmüz accepted, taking the throne as Ri'erha II, and Pethmil retired to spend the last years of his life in exile on Tenedos.