Con O'Neill is a distinguished English actor whose career spans over four decades across stage, television, and film. He is perhaps best known to international audiences for his powerful performance as Mickey in the original London production of Jonathan Larson's musical Rent and for his critically acclaimed role in the HBO series Chernobyl. Born in 1966 in Liverpool, England, O'Neill discovered his passion for acting at a young age and trained at the prestigious Royal Academy of Dramatic Art, where he honed the craft that would define his career.

O'Neill's early career was marked by a strong presence in British theatre, where he quickly established himself as a versatile and compelling performer. His breakthrough came in 1992 when he originated the role of Mickey in the West End production of Rent, earning widespread acclaim for his raw energy and emotional depth. This performance not only showcased his vocal abilities but also his capacity to inhabit complex characters, leading to a series of notable stage roles. He later appeared in Alan Bennett's The History Boys at the National Theatre, a production that would later be adapted into a film, and starred in Peter Gill's The York Realist, for which he received an Olivier Award nomination for Best Actor.

Transitioning to screen work, O'Neill built an impressive filmography with memorable roles in both television and film. He appeared in The History Boys alongside Richard Griffiths and Frances de la Tour, and later took on the role of Mr. Dursley in the stage adaptation of Harry Potter and the Cursed Child in London's West End. On television, he delivered a standout performance as Boris Shcherbina in the 2019 miniseries Chernobyl, a role that earned him widespread recognition and a Primetime Emmy Award nomination. His portrayal of the Soviet official grappling with the nuclear disaster's aftermath was praised for its nuance and humanity. He has also appeared in series such as Doctor Who, The Crown, and Vera, demonstrating his range across genres.

In recent years, O'Neill has continued to balance stage and screen work with remarkable consistency. He starred in the 2022 series The Last Kingdom as King Edward and appeared in The Batman as Chief Mackenzie Bock, further expanding his reach in blockbuster cinema. His commitment to his craft and ability to bring depth to every role have made him a respected figure in the industry. As of 2025, O'Neill remains active in both theatre and television, with several projects in development. His enduring legacy lies in his dedication to storytelling and his ability to connect with audiences through characters that resonate long after the credits roll.