Ianto Jones is a fictional character in the BBC television series Torchwood, played by Welsh actor Gareth David-Lloyd. A series regular, Ianto appears in every episode of the programme's first three seasons, as well as two crossover episodes of Torchwood's parent show, Doctor Who. Additionally, Ianto appears in Expanded Universe material such as the Torchwood novels and audiobooks, comic books and radio plays. Within the narrative of the series, Ianto begins as general support officer for Torchwood Three, a team of alien hunters stationed in Cardiff, and develops into an active field agent. Initially the regular character with the least screen time, Ianto's role expanded in response to growing cult appeal.

Reserved and efficient, Ianto was often used by writers to add humorous asides to the episodes' scripts. The character becomes the main romantic interest of Captain Jack Harkness (John Barrowman), who is the lead male of the series. Established to have had heterosexual relationships prior to the series, Ianto's story forms a part of the show's ongoing exploration of human sexuality. Expanded Universe material develops on Ianto's sexual orientation and the nature of the relationship with Jack, describing Ianto as bisexual and his feelings for Jack as genuine love. Additionally, writers have used these other media to explore Ianto's characterisation; for example, some stories elaborate on Ianto's backstory, or provide insight into his feelings.