Dr Martha Jones, later Martha Smith-Jones is the deuteragonist of Series 3 (2007) and a guest character in Series 4 (2008) of Doctor Who. She was a British physician who met the Tenth Doctor while in residency at Royal Hope Hospital in London when the hospital was transported to the moon by the Judoon, after which she began travelling with the Time Lord.
Unlike other companions, she not only fell in love with the Doctor but also declared her feelings. She decided to stop travelling with him as he failed to return that affection, but continued to have a number of adventures both with and without him, thanks to her work with UNIT and the Torchwood Institute.
She eventually fell in love with and married Mickey Smith (who was orignally the boyfriend Rose Tyler, who was a previous companion of the Doctor) and one time, they were saved by the Doctor (who was nearing his next regeneration) from a Sontaran.
In the 2020 short story "Farewell Sarah Jane", Martha attends Sarah Jane Smith's funeral alongside Mickey and their son August.