No, Harry Potter was not a Muggle. He was a Half-Blooded wizard born to a Pure-Blooded father and a Muggleborn mother. While his mother Lily Evans came from a Muggle family, his father James Potter was a descendant of one of the popular Pure-Blooded families of the Peverells. One of his old ancestors, Ignotus Peverell is believed to be the original owner of the Invisibility Cloak passed down to Harry as an inheritance.