Graham O'Brien is a fictional character created by Chris Chibnall and portrayed by Bradley Walsh in the long-running British sci-fi television series Doctor Who.

In the show's eleventh series, starting with the first episode, he served as a companion of the thirteenth incarnation of the alien time traveller known as the Doctor (portrayed by Jodie Whittaker) until the 2021 New Year's Special "Revolution of the Daleks".

[6] Whilst returning home after an unsuccessful session of teaching Ryan how to ride a bike, despite his insistence that he was "doing it, mate", Grace and Graham were trapped when a swarm of gathering coils attacked their train in search of Karl Wright, a fellow passenger.

[6] Believing the pair to be bonuses in the Rally of the Twelve Galaxies, Angstrom scooped Ryan and Graham out of deep space and transported them aboard her ship.

[9] The TARDIS deposited the Doctor and her companions in 1955 Montgomery, Alabama, instead of returning them to Sheffield due to large traces of Artron energy.

He defended them from the racism inflicted on them, even coming to Ryan's aid when Mr Steele slapped him for returning a glove to his wife Lizzie.

He and Ryan encouraged James Blake to leave his fishing spot on his day off after spreading a rumour of a black boycott.

After the giant spiders had been dealt with, Graham decided to join the Doctor in the TARDIS as he didn't want to just stay in his house and dwell on his grief.

The Doctor provided the two men with their own psychic paper as a parting gift and Ryan and Graham decided to continue investigating alien events and protecting the Earth together.

In "The Power of the Doctor," it's revealed that Graham has continued investigating alien activity on Earth, although Ryan is currently in Patagonia and unable to help him.

After burying Grace, Graham joins Ryan and Yaz in helping to teleport the Doctor back to her missing spaceship, but they are inadvertently swept along with her.

After their consequential adventure in "The Ghost Monument", the Doctor agrees to take Graham, Ryan and Yaz back to Earth.

They eventually return to Sheffield in "Arachnids in the UK", and Graham wrestles with his grief as he begins seeing apparitions of Grace in their home.

[14] In the series finale, "The Battle of Ranskoor Av Kolos", Graham is confronted by Tzim-Sha's return and vows to avenge Grace's death, despite the Doctor's threat that she won't travel with a killer.

[17] In September 2018, three Series 11 tie-in novels were announced, all of which feature Graham O’Brien – The Good Doctor, Molten Heart and Combat Magicks.

[22] In the Radio Times, critic Paul Jones wrote that "of the rest of the Tardis team, Bradley Walsh as Graham is the stand-out, a really believable and likeable character and able to convey such a range of emotion in just a few looks".