Historically known as Rhages (/ˈreɪdʒiːz/), Rhagae, and Arsacia, Ray is the oldest existing city in Tehran Province.

One of the etymologies proposed for the name of the Radhanites—a group of merchants, some of Jewish origin, who kept open the Eurasian trade routes in the early Middle Ages—links them to Ray.

Arad mountains (کوه آراد): located in the center of Ray County, on the border between Kahrizak and Fashapoye parts, its height is 1428 meters.

[6] This range also appears in a map dated to 1307 AH, during the era of Naser al-Din Shah Qajar, drawn by two Iranian engineers of the time.

In the book Detailed Geography of Iran, Mount Arad is mentioned with the name of mountains Hasanabad and Kanargard (حسن‌آباد and کنارگرد).

Kūh-e Qarah Bologh (کوه کورابلاغ): This mountain is located at the intersection of four cities, Zarandiyeh, Saveh, Ray and Qom.

This river runs in a northwest-southeast direction throughout Ray City and after joining one of the branches of Jajroud flows into the salt lake.

It is recorded in Ancient Greek as Rhágai (Ῥάγαι) and Rháges (Ῥάγες) and in Latin as Rhagae and Rhaganae.

Agricultural settlements were long established as part of the Central Plateau Culture on local foothills such as that of Cheshme-Ali in northern Ray, which dates back to around 6,000 BC.

[2] The city remained an important site under the Parthians, as demonstrated by its many coin mints, under the name of ῬΑΓΑΙ/Ῥάγαι (the Greek form of Ragā/Raγā).

[17] According to Isidore of Charax, under the Parthian and Seleucid eras, Ray was surrounded by the province of Rhagiana together with four other cities.

[18] Ray was amongst the bases used by the Parthians to thwart nomadic attacks and to occasionally invade the Central Asian steppe.

[20] Siyavash, the son of Mehran and the last King of Ray in the Sasanian Empire, was defeated fighting the Muslim invasion in 643.

[10] By the time of the Abbasid Caliphate, Ray was considerably restored and expanded into a new city named Mohammadiya.

A Tower of Silence, where Zoroastrians of after the Muslim conquest had come to put the bodies of the dead in the open, was built by a wealthy inhabitant of Ray on a hill in the tenth century.

[21][22] Also dating to the tenth century is the Bibi Shahrbanu Shrine, which is the site of a former Zoroastrian temple dedicated to Anahita, the ancient Iranian goddess of the waters.

A zealous Sunni, Mahmud had large numbers of the local population, consisting of Ismailis and Mazdakites, crucified and many books of the great library of Rayy burned as he considered them heretical.

[10] It had developed a great urban market that also benefited its neighboring regions, including the once small town of Tehran,[11] and had become a remarkable center for silk weaving.

Amin Razi, a Persian geographer from Ray who lived by the time of the Safavid dynasty, attests to the "incomparable abundance" of the gardens and canals of his hometown.

[34] Thus, between the years 1886 and 1888, under the reign of Qajar ruler Naser al-Din Shah, Ray became the first place in Iran to be connected to the capital by a railway.

Following the 1979 Revolution, the Mausoleum of Reza Shah was destroyed under the direction of Sadegh Khalkhali, an infamous cleric who was appointed by Ruhollah Khomeini as the head of the newly established Revolutionary Courts.