Quirinus is an ancient Roman deity. In the era of Augustus in Rome, Quirinus was once mixed with Janus as Janus Quirinus. His name comes from "quiris (spear/spear)".

Quirinus is highly likely to be the primitive god of war among the Sabins. Modern scholars mostly believe that Quirinus was the protector of Roman soldiers during peacetime.

As the God of War of the Sabines, his altar was erected early on on on the Collis Quirinalis (one of the seven hills of Rome), and the Sabine's altar was very close to the location where Rome was ultimately established. When the Romans settled there, they incorporated Quirinus into their earliest mythological system (before being influenced by Greek mythology). In the second half of the 1st century BC, Quirinus was considered a deified Roman builder and a wolf raised child named Romulus.
So he quickly became an important deity at the time, along with Mars (the agricultural god at that time) and Jupiter, known as the Capitoline Triad of the Collis Capitolinus (also one of the seven hills of Rome).
Of course, later on, Quirinus became much more numerous than before, losing his position as the three gods of Capitolini (replaced by Juno Juno and Minerva), and the Romans gradually diluted him in the mythological system, which was beneficial for other gods who were more personal and mysterious. In the end, he was only worshipped by his worshippers.

In early Roman art, he was depicted as a bearded figure dressed in religious attire and armor. Of course, it almost never appeared in works related to the Roman mythological system later on. He is often described as related to myrtle.

Quirinalia is celebrated on February 17th, which is the festival of Quirinus. It originated from his confusion with Romulus and is actually a festival commemorating Romulus.

Even centuries after the fall of the Roman Empire, the Mount Quirinale in Rome, named after him, was still associated with power. It was once chosen as the location of the palace and later became the residence of the President of the Italian Republic.