Melody Pond

Professor River Song was a human archaeologist. She is assumed to have an unusually intimate relationship with the Doctor, since she was the only person known to know his real name.

Biography
River Song was an archaeologist from the 51st century already highly familiar with the Doctor when they first meet (from his perspective). She was, in fact, a future companion of his who travelled with him off and on. According to her, he trusted her implicitly. River's expedition to Library was financed by Felman Lux and was chartered to find out what disaster had happened there, 100 years previously, that had caused 4022 people to "die" or disappear. When her team ran into trouble during an expedition to a deserted library, it was only natural that River should try to summon the Doctor by sending him a message via psychic paper. The version of the Doctor who turned up had not yet met her. Though bewildered, he agreed to help River and her team.

River and the Doctor appeared to be very familiar, even considering the strong bonds the Doctor forms with his companions. She keeps a worn and battered diary whose cover looks very much like the TARDIS doors, apparently a journal of her travels with the Doctor. There is a suggestion that in the future the Doctor will carry a similar journal, as she comments about needing to "compare" diaries. She carried an upgraded version of the sonic screwdriver which "her" version of the Doctor had given her.

As the situation in the Library deteriorated, River realised she must prove to the Doctor that she is (or will become) someone he trusts completely and with profuse apologies, she whispers his true name into his ear. The Doctor is stunned that she would know this information, and River succeeds in winning his trust.

River physically died when she chose to sacrifice herself in order to stop the Doctor from sacrificing himself in order to save Donna and the other 4022 people trapped in the Library. She pleaded with him to not try and change history, not to change one moment of what is to come for them.

After saving all the trapped people, the Doctor realized his future self must have given her his sonic screwdriver for a reason. Inside he found a data chip, which contains River's Data Ghost. The Doctor saved her by uploading her into the virtual world contained in The Library's data core. CAL, the library's data core controlled by a human girl wired into its mainframe, also managed to save the data ghosts of all of River's dead archaeological team, so she would have company in the virtual world. (DW: Silence in the Library/Forest of the Dead)

Other information
River Song seemed to take shorter trips with the Doctor, living a more or less normal life between trips, rather than have one extended trip with the Doctor and never see him again after parting ways.

The Doctor indicates that there is only one event wherein he would or could tell her his true name.

When Davros said to the Doctor that "Everywhere you go there are always deaths" River appears in a flashback, as the Doctor has flashbacks over those who have died during his travels. (DW: Journey's End)

Song appears to have knowledge of Time Lord anatomy, including knowledge of regeneration. She also indicates that destruction of both of the Doctor's hearts is a circumstance after which regeneration is not possible.

River Song's Timeline

 * River Song meets the Doctor for the first time


 * River Song and the Doctor picnic at Asgard


 * River Song and the Eleventh Doctor are present at the Crash of the Byzantium.


 * River Song and the Doctor travel to the End of the Universe


 * The Doctor tells River Song his name.


 * River Song, for some reason, obtains handcuffs.


 * The Doctor, with a new haircut and a suit, visits River Song and takes her to see the Singing Towers of Darillium. He gives her his Sonic Screwdriver.


 * River Song sends the Doctor a message on the Psychic paper, asking him to come to the Library. (DW: Silence in the Library)


 * The Tenth Doctor, whilst travelling with Donna Noble comes to the Library in the 51st Century and meets River Song for the first time, when they face an infestation of Vashta Nerada within the Library. River Song proves to the Doctor how important she will be to him by uttering his name in his ear. (DW: Silence in the Library)


 * River Song sacrifices herself to save the Doctor and the Library. (DW: Forest of the Dead)


 * The Doctor beams River Song from a Neural Relay in her sonic screwdriver into the Library's Data Core. (DW: Forest of the Dead)


 * River Song's brainwaves live on in the virtual world inside the Data Core, containing CAL and Doctor Moon. She is reunited in this virtual world with her crew mates, Proper Dave, Other Dave, Anita and Miss Evangelista, whose brainwaves must have also been added to the Data Core. (DW: Forest of the Dead)

Behind the Scenes
It has been revealed that River Song will be returning in Series 5 in a story featuring the crash of the Byzantium.