Irene of Hungary (Hungarian: Szent Piroska, Greek: Αγία Ειρήνη της Ουγγαρίας, born Piroska; 1088 – 13 August 1134) was the Byzantine empress by marriage to John II Komnenos. The Byzantine Empire was at its height during this period, and her husband, John II, has been regarded as the greatest of the Komnenian emperors. She is venerated as a saint in the Eastern Orthodox Church and is sometimes listed as the Blessed Irene of Hungary (post-congregation) by some Catholic sources, but not by others. Although Hungary belongs to the Western Catholic Church, Piroska is venerated there as a Hungarian saint.

The original Hungarian form of her name cannot be determined with complete certainty, it first mentioned in the Chronicon Pictum, which refers to the daughter of Saint Ladislaus as Pyrisk. If Pyrisk is not a rendering of the name Piros but of Piroska, it is unclear why the final -a is omitted, which would have made the name declinable in the Latin text, and why an i appears in place of the o. If the name is instead derived from the Latin Prisca, the omission of the final -a is even more difficult to explain. There is no trace among the Árpáds of the veneration or even knowledge of Saint Prisca, moreover, both the name Prisca and Piroska are otherwise unknown in the Árpád period. The Latin name Prisca, literally meaning 'ancient', but implying 'serious' or 'grave' behaviour.

On her deathbed, in accordance with the Byzantine customs of the era, she took monastic vows, became a monastic (nun), taking on the monastic name Xene.

Piroska was born in 1088, the daughter of King Ladislaus I of Hungary and Adelaide of Rheinfelden. She was orphaned at an early age, while still a child: her mother died in 1090, and her father died on 29 July 1095. King Ladislaus I was succeeded by his nephew, Coloman. Piroska spent her youth under the supervision and at the court of her cousin, King Coloman of Hungary, known as Coloman the Learned, where she received a thorough education. At the age of 16, she met the customary fate of medieval princesses, becoming the fiancée of a man she had never personally met, and shortly thereafter she became his wife in 1104. The chosen groom was the dynastic heir of the Byzantine Komnenos dynasty.

In an effort to improve relations with Emperor Alexios I Komnenos of the Byzantine Empire, King Coloman of Hungary arranged the marriage of his cousin, Piroska, to John "the Beautiful" Komnenos, the eldest son of Alexios I and Irene Doukaina, who had been co-ruler with his father since 1092 and was expected to succeed him. In her historical work, Anna Komnene mentions a treaty between Alexios and Coloman in which the emperor refers to the Hungarian king as sympentheros (co-father-in-law), however, this term simply reflects the dynastic marriage of the Hungarian princess and the fact that the family tie served to strengthen political relations between the two rulers. The negotiations were successful and Piroska married John in 1104. The marriage was recorded by Joannes Zonaras and John Kinnamos. During the marriage, John was already the designated heir to the throne, so it was known that Piroska would later be crowned Empress of the Roman Empire (the term "Byzantine Empire" is a modern historiographical designation, at the time, the state was regarded as the Roman Empire, and its people called themselves Romans).

When the Hungarian princess arrived in her new homeland, the Komnenos dynasty and Byzantium itself was at its height. Her husband, John II, succeeded his father in 1118 and was later regarded as the greatest of the Komnenian emperors. Upon her settlement in Constantinople, Piroska was renamed Irene. As Byzantine empress, she was required to convert to the Eastern Orthodox faith, a name also borne by her mother-in-law, Irene Doukaina, as well as several other Byzantine empresses of the time. Greek authors generally mention her foreign origin, which was unusual for the period, as she was the first Western empress to sit on the Byzantine throne in a long time. A lifelong and harmonious relationship developed between John and Irene, as attested by numerous contemporary written sources.

Greek sources record that she gave birth to eight children, four sons and four daughters. In 1106, she gave birth to twins in Thessaloniki, Alexios and Maria. Irene's fourth and youngest son, had been born in 1118, the very year his parents ascended the throne, he later inherited the imperial crown from his father as Emperor Manuel I Komnenos (1143–1180). The contemporary Byzantine writer Theodore Prodromos composed a poem for the 1119 coronation of the imperial couple's first son, Alexios Komnenos, as co-emperor. A substantial portion of the work is devoted to the praise of the empress, with Irene of Hungary's lineage celebrated in highly extravagant terms. He described her as the "Mistress of the entire West", presenting the imperial union in an almost cosmic dimension as the symbolic unification of East and West.

Foreign delegations were frequently received at the court of Irene, she welcomed pilgrims from the Holy Land as well as envoys from Hungary, and on several occasions acted as a mediator in political affairs between the Kingdom of Hungary and the Byzantine Empire. During the reign of King Stephen II of Hungary (1116–1131), the son of King Coloman, Byzantine–Hungarian relations deteriorated. Between 1127 and 1129, a Byzantine–Hungarian War was fought, partly due to injuries suffered by Hungarian merchants, and partly because the Byzantine court had granted asylum to the blinded Prince Álmos, the uncle of Coloman. During the reign of King Béla II of Hungary, son of Álmos, a renewed period of peace prevailed between the Kingdom of Hungary and the Byzantine Empire.