For real?

Partially. The persians attempted to invade Greece several times and there was a battle between around 300 spartans the Persian military. What happened was Xerxes (who believed he was a god) decided to take the back way into Greece through the mountains (think macedonia, serbia, etc) the problem was the greeks somehow found out and sent an army. The reason the greeks were so successful is they were fighting in such a small space, they could easily pick the Persians off, kind of like Pizarro did when the Spanish invaded peru.

Somewhat on facts. There was really 300 people that defended their city against a whole army. What's not true is that they wore bronze armor instead on the leather speedos in the movies

It is based on facts, but there is also some dramatic interpretation. The Spartans did defend their land against the Persians. The movie does not mention this, but there was actually a second Greek leader who had just as important a role as Leonidas. He defended Greece against the Persians from a different location. Also, the fighting seens are not totally accurate. Although they look stunning flying through the air, the Spartans would never break rank like that. They stayed in the line formation while fighting, which was their strength. Overall the movie does present a fairly accurate depiction of what happened, but there are some details that have been changed/modified for dramatic effect.

The movie 300 was based on a lot of facts but like most movies they have to add in other details to keep the audience interested. For example the oracles were never real. They did however like most countries did a pre-selection of their children for those who where healthy enough. But overall the movie was somewhat accurate.

The story was based on a real battle, The battle of thermopyle. King leonidas is considered as the descendant of hercules. The battle took place inb thermopyle. Leonidas's army succedde over the initial waves, but then he was killed and his head were cutoff. But finally the spartans succeded.

the story were this is base is real but the rest its just show business