River Song's Doctor Who timeline is presented completely out of sequence, but what would it look like in chronological order? By it's very nature, Doctor Who is a time-bending and history-meddling entity and some of its most complicated tales require a little reflection to piece all the winding time streams into one cohesive narrative. This is never more apparent than during Matt Smith's era, at which time Steven Moffat ramped up the complexity of Doctor Who considerably, and one significant contributing factor in this shift was the regular addition of Alex Kingston's River Song.
First introduced during the Tenth Doctor's reign, River Song first appeared to the Doctor in "Silence In The Library" and clearly knew the Time Lord very well. Unfortunately, the Doctor had no recollection of ever meeting River, as she had only encountered future regenerations of the Doctor. Since Doctor Who is presented through the title character's own chronology, River Song's time-jumping antics fall seemingly at random, and the two characters regularly have to compare diaries in order to feel out where they stand in each other's timeline.
River's story begins with Eleventh Doctor companions, Amy Pond and Rory Williams. The pair get married and conceive a child on the TARDIS. With previous assistants evidently not feeling the need to copulate between episodes, this is the first time a baby is made while travelling through a time vortex, and this unusual setting gives the unborn child some of a Time Lord's power.
Meanwhile, the Silence had heard the prophecy of Doctor Who's first question and decided the Doctor needed to die in order to protect the universe from a second Time War. The Silence resolve to use Amy's unborn, time sensitive child as a weapon against the Doctor, kidnapping Karen Gillan's character during pregnancy, stealing the child away (as seen in "A Good Man Goes To War") and raising her with a single purpose: kill the Doctor. During this phase of her life, young Melody Pond was placed in a spacesuit and first attempted to carry out her mission in 1969 U.S.A., but failed.
Melody somehow escapes The Silence following this botched assassination and finds herself in New York, where she regenerates into Mels. Under her new guise, Mels finds her way back to Amy and Rory (when both are just children) and the trio grow up as friends, remaining close even into adulthood and their adventures with the Doctor. In "Let's Kill Hitler," Mels finally manages to tag along on a TARDIS trip, but is killed by a stray bullet, regenerating into the recognizable Alex Kingston version of River Song.
As an adult, The Silence finally catch up with River and force her back into the spacesuit to kill the Doctor, this time in 2011. River sabotages the attempt, breaking the timeline apart with her refusal. In this new alternate reality, the Doctor and River marry and restore the natural flow of time. While River laments that she must kill the Doctor or else risk the entire universe, the wiley Gallifreyan manages to escape death by replacing himself with a Teselecta unit.
Since the Doctor's survival must be kept secret, River is imprisoned in the Stormcage facility on charge of his murder, however, she regularly escapes and enjoys trips in the TARDIS with her husband. It's during this period that many of River's adventures with the Eleventh Doctor occur, including "The Time Of Angels" and "The Pandorica Opens." This era of River also visits her parents at various points to help explain the events of their present, such as when Melody is taken as a newborn baby in "A Good Man Goes To War."
After the Doctor erases himself from history, River's crime ceases to exist, and she is released from Stormcage. At this point in River's timeline, the events of "The Angels Take Manhattan" occur, marking the final occasion she would see her parents before they were caught by the Weeping Angels. Excluding post-death and audio book adventures, this is also the final confirmed time River sees the Eleventh incarnation of the Doctor.
She does, however, meet Peter Capaldi's Twelfth Doctor in Christmas episode, "The Husbands of River Song," where the couple spend 24 years together.
Finally, River heads to the library where she'll partake in her last adventure, meeting the Tenth Doctor and fighting the Vashta Nerada, before sacrificing herself. The events seen in "The Name of the Doctor" occur after River's death, with the character merely a ghost.
Doctor Who season 12 premieres in 2020 on BBC One and BBC America.