Nancy -  A young prostitute and one of Fagin’s former child pickpockets. Nancy is also Bill Sikes’s lover. Her love for Sikes and her sense of moral decency come into conflict when Sikes abuses Oliver. Despite her criminal lifestyle, she is among the noblest characters in the novel. In effect, she gives her life for Oliver when Sikes murders her for revealing Monks’s plots.
Mr. Brownlow -  A well-off, erudite gentleman who serves as Oliver’s first benefactor. Mr. Brownlow owns a portrait of Agnes Fleming and was engaged to Mr. Leeford’s sister when she died. Throughout the novel, he behaves with compassion and common sense and emerges as a natural leader.
Bill Sikes  -  A brutal professional burglar brought up in Fagin’s gang. Sikes is Nancy's pimp and lover, and he treats both her and his dog Bull’s-eye with an odd combination of cruelty and grudging affection. His murder of Nancy is the most heinous of the many crimes that occur in the novel.
The Artful Dodger -  The cleverest of Fagin’s pickpockets. The Dodger’s real name is Jack Dawkins. Though no older than Oliver, the Dodger talks and dresses like a grown man. He introduces Oliver to Fagin.

Charley Bates -  One of Fagin’s pickpockets. Charley is ready to laugh at anything.
Bull’s-eye -  Bill Sikes’s dog. As vicious as his master, Bull’s-eye functions as Sikes’s alter ego.
Monks -  A sickly, vicious young man, prone to violent fits and teeming with inexplicable hatred. With Fagin, he schemes to give Oliver a bad reputation.
Agnes Fleming -  Oliver’s mother. After falling in love with and becoming pregnant by Mr. Leeford, she chooses to die anonymously in a workhouse rather than stain her family’s reputation. A retired naval officer’s daughter, she was a beautiful, loving woman. Oliver’s face closely resembles hers.
Mrs. Corney -  The matron of the workhouse where Oliver is born. Mrs. Corney is hypocritical, callous, and materialistic. After she marries Mr. Bumble, she hounds him mercilessly.
http://www.sparknotes.com/lit/oliver/characters.html