While Isis is a rather important goddess, her exact origins are a little hazy, although she is thought to have come from the Nile Delta. On the other hand, she was different from other Egyptian deities and did not highlight a central cult at any time of her worship. The first time Isis is mentioned in literary texts is around the Fifth Dynasty of Egypt, which is where initial inscriptions have been uncovered.
History shows that her cult grew in prominence late in Egyptian history, as it started to absorb the cults of numerous other goddesses. Over time, her recognition would eventually spread outside of Egypt and inhabit the Middle East and the Roman Empire. Temples started to sprout up in her honor in locations as far as the British Isles. As far into history as the 6th century, the worship of Isis was seen in Christian Europe.
The majority of Egyptian deities began in local circles and as history evolved, localized centers of worship became established. Most of them were situated in major cities and towns and were mostly concentrated in the hometowns connected to a deity. Yet, Isis was rather important in time, but there shows no traces of overwhelming cults in her honor.
Early history doesn’t show any temples dedicated in her honor. Worship on an individual basis started to take shape as late as the 30th Dynasty, where Isis was seen as and started to become worshipped with other goddesses. It was not uncommon to see Isis worshipped at the same time as Horus (her son) and Osiris (her brother slash husband). You should note that a marriage between a brother and a sister was typical in an ancient Royal family because they believed it kept their royal bloodline intact. While Isis was an Egyptian goddess, the civilization that would pay the best homage to her was the Romans.
Temples would extends to other parts of the world, and in some locations, her cult takes over the worship of other goddesses, as seen in the replacement of Semitic goddess, Astarte. During the Hellenic era, since Isis represented a protector and mother, especially when it came to becoming the patron goddess of sailors. Therefore, you will see a lot of references to Isis throughout the Greco-Roman world, as she emerges as one of the most important of the mysteries pertaining to religion.
Classical writers also catch a hint to the allure of Isis and start to make note of her cults, temples, and rites. Over time, temples in her honor begin to surface in Greece, Rome, Iraq, and even in northern locales like England, where the remains of a temple around Hadrian’s Wall has been uncovered. The British Isles would construct a temple on the River Thames , close to Southwark. In Rome, Isis took on many different names, including the Queen of Heaven. Herodotus would also group Isis with the Greek and Roman goddesses of agriculture (Demeter and Ceres). As part of Yoruba mythology, she is known as Yemaya.