Thomas Souness Hamblin (14 May 1800 – 8 January 1853) was an English actor and theatre manager. He first took the stage in England, then immigrated to the United States in 1825. He received critical acclaim there, and eventually entered theatre management. During his tenure at New York City's Bowery Theatre he helped establish working-class theatre as a distinct form. His policies preferred American actors and playwrights to British ones, making him an important influence in the development of early American drama.

Although he was known as a fair (if shrewd) businessman, Hamblin's reputation was marred by his well-known womanising and brawling. He had affairs with several up-and-coming actresses at his theatre, and he assaulted at least two newspaper editors who had published unflattering stories about him. His behaviour eventually cost him his first wife and resulted in one conviction for assault.

Hamblin was born in Pentonville, England. He apprenticed in a London business but changed course after a successful performance as Hamlet in a school production. By 1815, he had made his professional debut as a ballet dancer at London's Adelphi Theatre. He toured the British Isles over the next eight years, performing at venues such as the Drury Lane Theatre (for manager Stephen Kemble) and Sadler's Wells Theatre. He married Elizabeth Blanchard, a popular actress and daughter of actor William Blanchard and half-sister of actor/playwright E. L. Blanchard. Hamblin had two children by his first wife: William Henry Hamblin Jr. (stage name "Thomas Hamblin Jr") and Elizabeth "Betsey" Hamblin.

Despite some success he had still not established himself with the London critics when, in 1825, Hamblin and his wife left England for the United States. Hamblin took the stage at New York's Park Theatre in early November, where he tackled a number of roles: Hamlet, Macbeth, Othello, Petruchio, Pierre, Rolla, the Stranger, William Tell, and Virginius. Later that month, he appeared opposite Edwin Forrest at the Albion Theatre.

Critics praised Hamblin; the Albion calling him "a very excellent actor". Theatre historian T. Allston Brown attributed his success to these factors:

As an actor, he possessed the valuable accessories of a fine person, a good voice, and careful education. . . . In person he was tall and commanding, but so admirably proportioned as in a measure to conceal his almost towering height. Deep set eyes as black as jet were surmounted by a lofty brow, crowned by clusters of curling dark hair in such rich profusion as is seldom seen, except in some of the models which have been handed down to us from remote antiquity. To see him dressed for Brutus, Coriolanus, or Virginius was a study for a painter.

Francis Wemyss disagreed at least in part, saying that Hamblin's acting was "more than balanced by the husky, disagreeable tones of his voice, which always gave the appearance of hard labour to everything he undertook."

Hamblin began his tenure as manager of New York's Bowery Theatre with partner James H. Hackett in 1830. Hackett left a month later, and Hamblin obtained the lease and rebuilt when the theatre burnt down later that year. Hamblin catered to the tastes of the rowdy audiences of New York's Bowery district. These "Bowery B'hoys" were working class, primarily male, and socially conservative., and Hamblin accordingly staged blackface performances, circus acts, English farce, American melodrama, and Shakespeare to please them. Hamblin himself preferred upper-class entertainments like ballet and opera; nevertheless, he relegated these to infrequent bookings. Under Hamblin, American working-class theatre, emphasising brilliant spectacle and plot-based narrative, emerged as a form in its own right.