Petunia Dursley is Harry's aunt, and sister to Harry's mother, Lily. Not that she likes to talk about her... No, Petunia prefers to keep the family home spick and span and spoils her son (Dudley) rotten with presents. As for Harry, she is much less kind to him. Much like her husband, Vernon, she seems to hate the idea of magic and much prefers life when Harry is stuck in his cupboard under the stairs.
In the books, Aunt Petunia has blonde hair, while her sister Lily had red hair.