Gambit (Remy LeBeau) debuted in 1990's Uncanny X-Men #266, at which point he was already an adult thief.  He appears in various scattered flashbacks before that point, most of them from the shortlived Gambit vol 3, but also including the first information about his background in X-Men vol 2 #8, and flashbacks to his involvement in the Mutant Massacre in Uncanny X-Men #350.

Chris Claremont's X-Men: The End miniseries, set in an alternate timeline, claims that Gambit is the third Summers brother, and a creation of Mr Sinister.  Marvel do not regard that miniseries as having any status in mainstream continuity, and it seems likely that it will be firmly discredited in 2006 with the publication of a conflicting explanation of the third Summers brother.

GAMBIT vol 3 #23 (flashback)
Jean-Luc LeBeau steals the infant Remy from his cot in a New Orleans hospital...

GAMBIT vol 3 #1, page 15 (flashback)
...and takes him to the Antiquary, a member of the Thieves' Guild, who will raise the child.

GAMBIT vol 3 #1, page 16 panel 2 (flashback)
Generic shot of young Remy as a member of "Fagan's Mob", the Antiquary's children.

GAMBIT & BISHOP #2 (flashback)
Aged "about six", Remy finds the Witness's home in a New Orleans Mausoleum.

GAMBIT vol 3 #25 (flashback)
As a "li'l mutant scamp", Remy breaks into the home of powerful businessman Mondo Mastiff, only to be caught.  Mastiff lets Remy go as a favour to his daughter.

GAMBIT vol 3 #1, pages 16-17 (flashback)
Aged either 8 or 10 (the dialogue is inconsistent), Remy meets Bella Donna for the first time when he saves her from rebel Assassins Guild members.  They swiftly become friends.  A few days later, Remy tries to pick Jean-Luc's pocket, but gets caught.

GAMBIT vol 3 #6 (flashback)
Aged 15 and 6 weeks, Remy accompanies 13-year-old Etienne Marceaux on his "tilling", a theft assigned by the Thieves Guild.  They raid Candra's home and get caught.  Candra sends them to be kept as slaves by the Pig.  Remy escapes, but Etienne is killed.

X-MEN vol 2 #33 (flashback)
Remy is 17 (and due to marry Bella Donna on his 18th birthday in four months time).  The Thieves Guild send him to Paris to steal a pendant, and obtain membership of their Elite.  Rather than steal it, Remy cynically seduces Genevieve Darceneaux, who holds the pendant.  Sabretooth is also hired to recover the pendant, and Remy encounters him for the first time.  Sabretooth gets the pendant and kills Genevieve.

GAMBIT vol 3 #1, page 17 panel 5 (flashback)
One week after Remy's birthday, he and Bella Donna get married.

X-MEN vol 2 #8, page 18 panel 2 (flashback)
After the wedding, Remy and Bella Donna kiss.

X-MEN vol 2 #8, page 18 panels 3-4 (flashback)
Remy kills Bella Donna's brother Julien in a swordfight.  Remy is banished from New Orleans in an attempt to maintain the non-aggression pact between the Thieves and Assassins' Guilds.

WOLVERINE/GAMBIT: VICTIMS #3 (flashback)
Remy comes to London for the first time and helps police officer Alexandra Davies to arrest Yukio (who had previously tried to frame Remy for her crimes).

UNCANNY X-MEN #350, pages 2-4 (flashback)
Gambit meets with Mr Sinister after recruiting the Marauders, and asks for his pay.  Sinister pressgangs him into showing the Marauders to the Morlock tunnels.

UNCANNY X-MEN #350, page 28 (flashback)
Gambit and the Marauders prepare for the mission.

UNCANNY X-MEN #350, page 31 panels 1-6 (flashback)
Gambit shows the Marauders (or at least some of them) to the Morlock tunnels.  He is shocked to learn that they are killing the Morlocks, rather than abducting them for experimentation as he had been led to expect.  He tries to intervene, but is nearly killed by Sabretooth.  (This flashback also places Gambit behind the scenes in Uncanny X-Men #210.)

GAMBIT vol 3 #7, page 8 (flashback)
Gambit saves Marrow from Sabretooth.  He protests to Scalphunter (his only friend in the Marauders), and then leaves.

UNCANNY X-MEN #350, page 31 panel 7 (flashback)
Gambit flees the tunnels, clutching Marrow.

UNCANNY X-MEN #266
Gambit debuts, meeting Storm in Illinois.  (NB: Strictly speaking, Gambit's first published appearance was in Uncanny X-Men Annual #14, due to some very strange scheduling on Marvel's part.  However, this was intended to be the first Gambit appearance to ship.)

Revised: 30 December 2005