"Muggles" are non-magical people in the parlance of the Wizarding World. Muggles are for the most part oblivious to the entire society of magical people which exists alongside their own. Part of the reason for this is that Muggles simply don't believe that magic exists, which means they find non-magical reasons for the things that happen to them
People
Vernon Dursley - director of a firm that makes drills, no neck, thickset and bullheaded
Petunia Dursley (maiden name: Evans) - Lily Potter's sister, definitely not magical - long neck, horsey teeth; always spying on neighbors, fanatic about neatness, thinks Dudley's immense size is baby fat
Dudley Dursley
Mrs. Figg - neighbor, sometimes takes care of Harry
her cats: Tiddles, Snowy, Mr. Paws, Tufty
although Mrs. Figg isn't really a Muggle at all! (BP)
Piers Polkiss - friend of Dudley's
other friends: Dennis, Malcolm, Gordon
keeper of the reptile house in the zoo
zoo director
Aunt Marge - (Miss Marjorie Dursley, Vernon's sister)
Yvonne - Aunt Petunia's friend
Col. Fubster - looks after Aunt Marge's bulldogs when she's away (PA2)
Mr. and Mrs. Mason - Muggle parents of Hogwarts students
Dr. and Dr. Granger - Hermione's parents, who are both dentists
Seamus Finnegan's father (whose wife didn't admit that she was a witch until they were married)
Mr. Creevey - a milkman who has two sons who are wizards (CS)
on television: The Great Humberto, on Monday nights (SS3)
toothless old man - lends them his rowboat to get to the hut on the rock (SS3)
owner of the Railview Hotel (a woman) (SS3)
known inhabitants of Little Hangleton fifty years ago (c. 1940):
the Riddle family: Mr & Mrs, son Tom
Frank Bryce, Riddle's gardener, 28 at time of deaths (b. 1912)
the cook - told the pub that Frank was guilty, no doubt about it
the maid - found the bodies
Mr. Roberts and family (wife, two children) - campground manager who had a most peculiar couple of days recently, although he's forgotten all about it...
other campground manager: Mr. Payne
Jim McGuffin - weatherman on the evening news Vernon Dursley was watching on November 1, 1981
Ted - newsreader on the evening news, November 1, 1981
'Dodgy Dirk' - an inhabitant of Ilfracombe who insists to this day that a "dirty great flying lizard" attacked him on the beach. He is the only Muggle who seems to remember that attack by a dragon in Ilfracombe in 1932; all the other Muggles involved were given Memory Charms by a wizarding family which happened to be vacationing there that day. (FB)
Hetty Bayliss - lives in Norfolk; on 1 Sept 1992 she was sure she spotted a flying car while she was hanging out her wash (CS5).
Angus Fleet - lives in Peebles, a town in Scotland which is on a route between London and Hogwarts; Angus was mystified by a flying Ford Anglia on 1 Sept 1992 (CS5)
Brother Benedict - Franciscan monk from Worchestershire during the Middle Ages (FB)
had an encounter with a Jarvey but thought is was an overlarge ferrret, which insulted him then bit him on the nose
the friar - didn't believe Benedict that the ferret talked to him
§ Brother Boniface - made turnip wine
