When Rome conquered Greece, Rome adapted the Greek gods and myths into its own religion. The gods were given Latin names, but other than that, the gods and their stories remained the same. Everyone was required to honor Jupiter, however, who was the Roman equivalent of the Greek god Zeus, and was also considered the guardian of the Empire. One of the key features of Roman religion was that under the Republic, Rome allowed conquered territories to practice their own religions. 

After the time of Julius Caesar, the emperors were raised to the level of gods, and citizens were required to worship them along with the other gods. Shrines to the emperor Augustus were built in many places after his death, often showing him as equal with gods and goddesses. Later, several foreign gods became popular. Temples were set up to the Egyptian goddess Isis, who offered hope for the afterlife; and the Persian god of light, Mithras, was worshipped by a cult of soldiers. Some religious cults were made up only of women, such as the Vestal Virgins, who kept the flame for the goddess Vesta burning day and night.

The gods were to be feared, and sacrifice and offerings to them were routinely made by rich and poor alike. An offering was anything someone could afford, from a simple piece of jewelry to a whole temple. Augustus built the Temple of Mars the Avenger after he promised it to Mars, the god of war, if Mars would help him avenge the death of his father, Julius Caesar. Animal sacrifices were also common, with particular animals sacrificed to particular gods. The animals were sacrificed on an altar, which was basically a large carved box in front of a god's temple.