Aparan (Armenian: Ապարան [ɑpɑˈɾɑn], colloquially [ɑbɑˈɾɑn]) is a town in the Aparan Municipality of the Aragatsotn Province of Armenia, about 50 kilometers northwest of the capital Yerevan. As of the 2011 census, the population of the town was 6,451. As per the 2016 official estimate, Aparan had a population of around 5,300. As of the 2022 census, the population of the town was 5,803.

It is commonly believed that the name of Aparan is derived from the Armenian word Aparank, meaning a royal palace. However, throughout history, the town has been known by different names including Kasagh, Paraznavert, Abaran and Abaran Verin. Later, it was known as Bash Aparan (Բաշ Ապարան) until 1935, when the name was finally changed to Aparan.

In antiquity, the region of Aparan was known as Nig or Nigatun. The first reference to the town of Aparan was made by Ptolemy during the 2nd century. Ptolemy referred to the settlement as Casala (Κασάλα in greek); the Hellenized version of the Armenian name of Kasagh. It was the centre of the Nig canton of the Ayrarat province of ancient Armenia. Kasagh was under the administration of the Gntunik Armenian noble family, under the rule of the Arsacid dynasty of Armenia. The Gntunik princes founded the Basilica of Kasagh by the end of the 4th and beginning of the 5th centuries. It was originally within the grounds of the Arsacid (Arshakuni) palace of the kings of Armenia, located in the town.

Between the 9th and 11th centuries, Aparan was part of the Bagratid Kingdom of Armenia with the Gntuni princes being registered as vassal princes of the Bagratids. Starting from the 10th century, the settlement of Kasagh became known as Aparan. The new name was originated from the village of Aparank located in the Moxoene province of the Kingdom of Armenia, when some remains from the ancient Armenian monastery of Surp Khach of Aparan were transferred to the town of Kasagh.

From the mid 10th to the late 12th centuries, Aparan came under the control of various Muslim dynasties, namely the Kurdish Shaddadids and the Turkic Delimks (originating from modern-day Iran). During this period, Aparan was locally administered by the Armenian Pahlavouni princes. After the fall of Ani to the Byzantines in 1045, the Seljuks occupied most parts of the Armenian Highland by 1064. However, in the late 12th century, Aparan again came under Armenian rule with the establishment of Zakarid Armenia. The Zakarian rulers granted governance of the area to the Vachutian noble family who invested in multiple architectural works along the Kasagh valley. They ruled until the 14thth century, Armenia became part of the Ilkhanate of the Mongol Empire.

By the last quarter of the 14th century, the Aq Qoyunlu Sunni Oghuz Turkic tribe took over Armenia, including Aparan, before being invaded by Timur in 1400. In 1410, Armenia fell under the control of the Kara Koyunlu Shia Oghuz Turkic tribe.

Between 1502 and 1828, Armenia became part of the Persian state under the rule of Safaavid, Afsharid and Qajar dynasties, with short periods of Ottoman rule between 1578 and 1603 and later between 1722 and 1736.

In the 16th century, the Latin diocese of Nakhchivan's actual see (not the title) was moved to more central Aparan, closer to the actual Catholic communities. Around 1620, Pope Gregory XV instigated the founding of a Fratres Unitores (exclusive Armenian Dominican order branch) seminary in Aparan. The see was elevated on 21 February 1633 as non-Metropolitan Archdiocese of Nakhchivan, but diocesan activity seemingly effectively halted later that century. It would be suppressed in 1847, apparently vacant since 1765, as its faithful had fled the country during the devastating wars between the Ottomans and Safavids.