How many invasions of Greece were in the Persian Wars?

Answer 1

There were several minor fights in northern Greece, and a delaying action at Thermopylae. The main battles were the sea battle at Salamis and the land battle at Plataia.

Answer 2

It depends what you want to call Greece. It comprised 2,000 independent city-states stretching around the Mediterranean and Black Seas. And it depends what you call an invasion.

The Persians first put down a revolt in Asia Minor by Greek city-states within its empir 499-493 BCE. It sent a punitive expedition against Eretria and Athens for interfering in the Ionian Revolt 490 BCE. It sent an invasion to subdue the cities of mainland Greece 480-479 BCE. It fought several battles in Asia Minor and in the Islands of the eastern Mediterranean 478-449 BCE.