Robb is Eddard Stark's eldest true-born son and heir to Winterfell.
In season one, Robb serves as Lord of Winterfell after he father, Eddard Stark, moves to King's Landing to serve as Hand of the King. Robb runs Winterfell with Maester Luwin and helps comfort his brother, Bran, as he struggles with the news that he is permanently paralyzed from the waist-down after he was pushed out of a tower by Jaime Lannister. Using a gifted saddle from Tyrion Lannister, Bran is able to ride on a horse. One day while they were riding, several Wildlings ambushed Bran. Robb and Theon Greyjoy defeated all of the Wildlings, except for one, Osha, who was kept as a servant for the Starks.
After Ned was taken prisoner in King's Landing, Robb decided to round up his bannermen to get him back. Robb was not able to reach King's Landing in time to rescue his father. In response to Eddard's death. Robb declares war on the Lannisters in what would be called "The War of the Five Kings" (the other four kings being Renly Baratheon, Stannis Baratheon, Joffrey Baratheon, and Balon Greyjoy). Unlike the other four kings, Robb has no interest is sitting upon the Iron Throne, and instead wants complete control over the North, as well as the death of Joffrey as justice for the death of his father.
Robb's army is successful in strategically manipulating the Lanniser army. He is able to capture Jaime Lannister and wins over the support of several other houses, including House Tully, House Frey, and many other Northern houses.
At the start of the season two, Robb is clearly ahead in his war with the Lannisters. He's fought three battles with the Lannisters, and won them all. Tywin, who initially underestimated Robb's ability, is now focused on defeating him and retrieving his son Jaime. Robb, realizing he will need allies to defeat Tywin, sends Theon to speak with his father Balon Greyjoy, and his mother Catelyn to speak with Renly Baratheon. Theon's visit with his father backfires on Robb. After Balon refuses to give help to Robb, Theon decided to capture Winterfell to try to impress his father. Catelyn's visit to Renly is also unsuccessful. She attempts to broker peace between Renly and his brother Stannis, so they can unite against Joffrey. Instead, Stannis orchestrates to have Renly killed.
After the successful Battle of Oxcross, Robb meets Talisa Maegyr, a medic who catches his fancy. The two decide to marry, which conflicts with an oath Robb made with Walder Frey to marry one of Frey's daughters.
Robb is later faced with another difficult decision, this time regarding his mother. After a visit from Petyr Baelish, Catelyn is convinced to release Jaime Lannister in exchange for her two daughters, who she believes are both at King's Landing (Sansa Stark is still at King's Landing, but Arya is at Harrenhal for most of season two). Robb and his lieutenants are furious. He decides to send men to go re-capture Brienne, who has been tasked to return him to King's Landing, and Jaime.
Season three begins with Robb and his army marching on Harrenhal, hoping to catch the garrisoned Lannister units. Instead, the castle has been abandoned and the prisoners have all been killed. Robb keeps some of his units garrisoned in the castle, and has his mother held as a prisoner. Shortly, he releases his mother from prison as they move to Riverrun, the original home of Catelyn and her house the Tullys, for the funeral of his grandfather Hoster.
Later, Robb chastises his uncle Edmure for attacking Stone Mill, a move which cost Robb two-hundred men and a chance to kill Gregor Clegane. Edmure insists he was right in his actions, citing that he captured two of Tywin Lannister's nephews. Robb is still annoyed. The two Lannister boys are held in cells, and a shortly killed by Rickard Karstark, one of Robb's top allies. Rickard viewed the killing of the two boys as justice for the death of his two sons. who were both killed by Lannisters. Robb is furious and sentences him to death, ignoring the advice of his mother that he be left alive because of the importance of the Karstark troops to Robb's army. Robb ignores him and executes Rickard, exactly how his father taught him ("the man who passes the sentence should swing the sword").
Without the Karstark troops, Robb's army is in trouble. He hatches a plan to take Casterly Rock, the home of the Lannisters, with the help of House Frey. The Freys decide that in order to gain their loyalty and repair the damaged relationship between the two houses, Edmure Tully must marry one of Frey's daughters. Edmure reluctantly agrees and the Stark army moves to the Twins.
While waiting to meet Walder, Robb and Talisa spend the night together. Talisa informs Robb that she is pregnant. She later says that she wants to name him "Eddard." When Edmure marries one of Frey's daughters, the relationship between the Freys and the Starks appears to have been healed. However, things soon turn horrific.
After Edmure and his new wife are carried off for the bedding ceremony, the doors to the dining hall are locked. The band starts to play "The Rains of Castamere," a song that was written about Tywin Lannister's destruction of House Reyne of Castamere. A man with a knife comes from behind and stabs Talisa in the stomach several times. Crossbowmen appear from the top level of the hall and start to fire shots at Robb, Catelyn, and the other Stark soldiers inside. Other Stark soldiers have their throats cut by Frey soldiers. Outside, more Stark soldiers, and Robb's direwolf Grey Wolf, are killed. Robb, after surviving several crossbow shots, goes to hold his dying wife. Catelyn, also surviving several crossbow shots, holds Walder's wife with a knife to her neck, saying that she will kill her unless Robb is let go. Walder says he can just get another one, and Robb is stabbed by Roose Bolton, one of his bannerman. As he stabs Robb, he says that the Lannisters "send their regards." Catelyn cuts the throat of Walder's wife, and soon has her own throat cut.