Major characters:
- Miss Clarissa Harlowe: The title character of the novel. Clarissa is a young and virtuous woman who ends up falling victim to Robert Lovelace after he convinces her to run away with him and later rapes her. Feeling as though she has entirely lost the will to live after losing her virtue, Clarissa prepares herself for death.
- Robert Lovelace: The villain of the story and pursuer of Clarissa. Mr. Lovelace is seen as a vile and selfish character who refuses to stop lusting after Clarissa until he gets what he wants.
- Anne Howe: Clarissa's best friend to whom she continuously writes throughout the course of the story. Anne serves as Clarissa's confidant as the story progresses.
- John Belford: A close friend of Mr. Lovelace whom he writes to during the course of the story. However, as the story progresses, he slowly begins to side with Clarissa instead of Mr. Lovelace.
Secondary characters:
- James Harlowe, Sr.: Clarissa's father
- Lady Charlotte Harlowe: Clarissa's mother
- James Harlowe, Jr.: Clarissa's brother, bitter enemy of Robert Lovelace.
- Miss Arabella Harlowe: Clarissa's older sister
- John Harlowe: Clarissa's uncle (her father's elder brother)
- Antony Harlowe: Clarissa's uncle (her father's younger brother)
- Roger Solmes: A wealthy man whom Clarissa's parents wish her to marry
- Mrs. Hervey: Clarissa's aunt (Lady Charlotte Harlowe)'s half-sister
- Dolly Hervey: Daughter of Mrs. Hervey
- Mrs. Norton: Clarissa's nurse, an unhappy widow
- Colonel Morden: A man of fortune, closely related to the Harlowe family
- Mrs. Howe: The mother of Miss Howe
- Mr. Hickman: Miss Howe's suitor
- Dr. Lewin: One of Clarissa's educators, a divine of great piety and learning
- Dr. H: A physician
- Mr. Elias Brand: A young clergyman
- Lord M.: Mr. Lovelace's uncle
- Lady Sarah Sadleir: Half-sister of Lord M., widow, lady of honour and fortune
- Lady Betty Lawrance: Half-sister of Lord M., widow, lady of honour and fortune
- Miss Charlotte: Niece of Lord M., maiden lady of character
- Patty Montague: Niece of Lord M., maiden lady of character
- Richard Mowbray: Libertine, gentleman, companion of Mr. Lovelace
- Thomas Doleman: Libertine, gentleman, companion of Mr. Lovelace
- James Tourville: Libertine, gentleman, companion of Mr. Lovelace
- Thomas Belton: Libertine, gentleman, companion of Mr. Lovelace
- Capt. Tomlinson: The assumed named of a pander that aids Mr. Lovelace
- Mrs. Moore: A widowed gentlewoman, keeping a lodging-house at Hampstead
- Miss Rawlins: A notable young gentlewoman in Hampstead
- Mrs. Bevis: A lively widow in Hampstead
- Mrs. Sinclair: The pretended name of a private brothel keeper in London; pretends to be Lady Betty
- Sally Martin: Assistant of, and partner with, Mrs. Sinclair
- Polly Horton: Assistant of, and partner with, Mrs. Sinclair
- Joseph Leman: Servant
- William Summers: Servant
- Hannah Burton: Servant
- Betty Barnes: Servant
- Dorcas Wykes: Servant
