Yes, of course it is. Hint: if you have a question like this, just Google “Shakespeare [name of play] sources” and you will get the information you need. For Julius Caesar, it was Plutarch's Lives in North's translation of 1579. read more
Julius Caesar was the first historical Roman to be officially deified. He was posthumously granted the title Divus Iulius or Divus Julius (the divine Julius or the deified Julius) by decree of the Roman Senate on 1 January 42 BC. read more
Julius Caesar was definitely a real historical figure, Shakespeare wrote a lot of his plays based on real people (like the Henry plays). Julius Caesar was stabbed several times in the senate house and many of the events and people mentioned were real people and documented events. read more