Pjetër Losha was an Albanian clan leader in medieval Epirus. He belonged to the Losha fis (clan or tribe) and was the leader of a combined force of his own clan and the fis of Mazaraki and Malakasi. In 1360, he became Despot of Arta, Rogoi and the area of Amphilochia. He died in 1374 and was succeeded by his close ally, John Spata. The Chronicle of the Tocco is an important primary source for his life and the Albanians in medieval Epirus in general.
Losha's genealogy or birth date is unknown. He belonged to the Losha clan. The word lios means "pockmark" in Albanian. He was part of the Albanian attacks in the remnants of Byzantine Epirus. In 1358-59, Albanian clans overran the regional feudal rulers and established themselves under John Spata and Peter Losha. He had a son named Gjin. Losha led the Albanian force against Nikephoros II Orsini at the Battle of Achelous that won him the rule of Arta; he founded his domain around Arta with the help of the Mazaraki and Malakasi clans. The domains he gained after the battle also included Rogoi and Amphilochia, as mentioned in the Chronicle of Ioannina. In 1360, Simeon Uroš, the titular Serbian Emperor, in an attempt to avoid conflict with the Albanians and as an acknowledgment of their military strength decided to the leave the areas of Arta and Aetolia to Shpata and Losha. 
In 1366, Toma Preljubović succeeded Simeon as ruler of Epirus. His rule marked a renewal of hostilities in the region as from 1367 to 1370, Ioannina, the capital of Preljubović, came under constant siege and was blocked by the Mazaraki and Malakasi clans under Losha. A truce was signed when Peter's son John was betrothed to Thomas's daughter Irina. She died in the 1375 plague that affected the region and hostilities began again.
His estates included the Epirote cities of:
He had a son named Gjin, who married Irina Preljubović, the daughter of Thoma.
- Hammond 1976, p. 59 In 1358 the Albanians overran Epirus, Acarnania and Aetolia, and established two principalities under their leaders, John Spatas (shpatë in Albanian meaning a sword) and Peter Leosas (lios in Albanian meaning a pockmark.
- Epeirotica 2.220; cf. 222 f
- Sansaridou-Hendrickx 2017, p. 292 In 1360, avoiding conflict with the Albanian forces and admitting thus their military superiority, Symeon Uros left in their hands Aetolia, which was divided between two rulers belonging to the Albanian race (genos), namely Gjin Bouas Spatas, who became Despot of Acheloos and Angelokastron, and Peter Liosas who was made Despot of Arta, Rogoi and the region of Amphilochia.
- Nicol, Donald MacGillivray (1984). The Despotate of Epiros, 1267-1479: A Contribution to the History of Greece in the Middle Ages. Cambridge University Press. pp. 142–5. ISBN 9780521261906. Retrieved 3 February 2013.
- M. V. Sakellariou (1997). Epirus, 4000 years of Greek history and civilization. Ekdotikē Athēnōn. ISBN 978-960-213-371-2.
For the Albanian tribes of the Mazarakaioi and the Malakasioi, led by Peter Losha the despot of Arta,
- Fine, John Van Antwerp (1994). The Late Medieval Balkans: A Critical Survey from the Late Twelfth Century to the Ottoman Conquest. University of Michigan Press. pp. 351–2. ISBN 9780472082605. Retrieved 3 February 2013.
- Sansaridou-Hendrickx 2017, p. 294.
- Vizantološki institut 1994, p. 133:
и Петар Љоша је владао градовима Арта и Роге, а Ђин Буа Спата градо- вина Ахелој и Ангелокастрон; опширно о њима
- Fine, John Van Antwerp (1994). The Late Medieval Balkans: A Critical Survey from the Late Twelfth Century to the Ottoman Conquest. Ann Arbor, Michigan: The University of Michigan Press. ISBN 0-472-08260-4.
- Sansaridou-Hendrickx, Thekla (2017). "The Albanians in the Chronicle(s) of Ioannina: An Anthropological Approach". Acta Patristica et Byzantina. 21 (2): 287–306. doi:10.1080/10226486.2010.11879131. S2CID 163742869.
- Hammond, Nicholas (1976). Migrations and invasions in Greece and adjacent areas. Noyes Press. ISBN 9780815550471. Retrieved 4 February 2013.
- Jireček, Konstantin Josef (1911). Geschichte der Serben (in German). 1. Gotha, Germany: Friedriech Andreas Perthes A.-G.
- Mihaljčić, Rade (1975). Крај Српског царства (in Serbian). Belgrade: Srpska književna zadruga.
- Nicol, Donald MacGillivray (2010), The Despotate of Epiros 1267–1479: A Contribution to the History of Greece in the Middle Ages, Cambridge University Press, ISBN 978-0-521-13089-9
- Soulis, George Christos (1984), The Serbs and Byzantium during the reign of Tsar Stephen Dušan (1331–1355) and his successors, Dumbarton Oaks, ISBN 0-88402-137-8
- Vizantološki institut (1994), Recueil de travaux de l'Institut des études byzantines, 33, Naučno delo
- Vizantološki institut (1975), Zbornik radova, 16–18, Naučno delo