Doctor Who is a long-running British science fiction television series that first aired in 1963. The show follows the adventures of the Doctor, a Time Lord from the planet Gallifrey who travels through time and space in the TARDIS, a time machine that looks like a British police box on the outside but is much larger on the inside. The Doctor is frequently accompanied by various companions, and together they encounter a wide array of aliens, historical figures, and cosmic phenomena. The series is known for its ability to regenerate the Doctor's character, allowing a new actor to take on the role while maintaining continuity in the narrative. This has enabled Doctor Who to evolve over the decades, remaining popular across different generations of viewers.

The show has had a significant impact on British pop culture and has gained a global following. It has won numerous awards, including BAFTAs and Hugo Awards, and holds the Guinness World Record for being the longest-running science fiction television series. Doctor Who is celebrated for its creativity, storytelling, and the unique blend of science fiction with historical and contemporary elements. Over the years, it has tackled various social and moral issues, making it not just entertainment, but a reflection of the times in which it was produced.