Mercedes Jones is a fictional character from the Fox musical comedy-drama series Glee. The character is portrayed by actress Amber Riley, and has appeared in Glee from its pilot episode, first broadcast on May 19, 2009. Mercedes was developed by Glee creators Ryan Murphy, Brad Falchuk and Ian Brennan. She is a dynamic diva-in-training who refuses to sing back-up, and is a member of the glee club and was a member of the Cheerios at the fictional William McKinley High School in Lima, Ohio, where the show is set.

In the pilot episode Mercedes auditions for the glee club by performing "Respect" by Aretha Franklin. Due to Cheerios scheming, Mercedes develops a crush on Kurt, unaware that he is gay. She is hurt when he rejects her, but supportive when he confides his sexuality. After this, the two become especially close friends. Her father is a dentist. In The Rhodes Not Taken, when April Rhodes is trying to get the other Glee club members on her side, she teaches Mercedes and Tina how to shoplift; the two are later seen with conspicuously new clothes and accessories as they give Mr. Schuester their approval of April. Her rivalry with glee club star Rachel comes to a head in Sectionals, when she impresses the entire group with a powerful ballad. Rachel agrees that Mercedes should perform the solo in sectionals, but she loses the chance when the competition steals the song.

Mercedes also dreams of being a star, though it is usually Rachel who gets the solos and female lead. In the episode "The Power of Madonna" both Mercedes and Kurt express their frustrations to Mr. Schue and respond by joining the Cheerios cheerleading squad, planning to participate in both so they will have more opportunities in the spotlight. It is also noted at the end of the episode that both Mercedes and Kurt get solos during the number "Like A Prayer", showing that Mr. Schue was listening to their complaints.

In the episode "Home", Sue Sylvester tells Mercedes that she must lose ten pounds and wear the female Cheerios uniform, though Mercedes tries to explain that it "doesn't fit her right," and she'd rather wear the pants. After fainting in the cafeteria and being told by the doctor she has low blood pressure, Quinn Fabray enters the room and assures Mercedes she went through the same thing. From this point on, the two girls develop a friendship. At the end of the episode, during a pep rally, Mercedes sings the song "Beautiful" by Christina Aguilera, and most of the Cheerios and Glee Club members join her, thus proving to everyone that Mercedes is proud of herself. In "Laryngitis", Mercedes quits the Cheerios after a brief fling with Puck, saying the Glee Club taught her to be true to herself. In the episode " Funk", she invites Quinn to move in with her. In the episode "Journey", Mercedes was in the delivery room with Quinn when she had her baby.

Ryan Brockington for the New York Post has written that "the key to this show lies directly within the female leads", praising Riley as Mercedes and noting that in "Acafellas", Riley "finally got a chance to shine". Similarly, Tim Stack of Entertainment Weekly commented that the best aspect of "Acafellas" was the focus it placed on previously more minor characters such as Mercedes. Eric Goldman of IGN criticised Mercedes' actions in the episode "Ballad", in which Puck confesses to her he is the father of Quinn's baby, and Mercedes responds by telling him to leave Quinn alone. Goldman questioned: "Really? She doesn't think Finn should know he's not really the dad? She doesn't think Puck should be involved, given he actually is the dad? It was a really strange response, and given Mercedes is not generally written to be an unlikable, manipulative person (That's Terri!), I'm not sure how the writers thought this was a justified viewpoint for her."

Korbi Ghosh of Zap2it has named Mercedes' best moment as her performance of "Imagine" in the episode "Hairography", commending her as: "instead of overpowering their performance with her spectacular talents, she toned it down, allowing the deaf choir to truly shine as she humbly sang beside them, showing her support." Ghosh deemed her low point vandalizing Kurt's car in "Acafellas", commenting: "Mercedes has clearly got some anger and aggression issues — not to mention being a bit clueless... the boy is into other boys, hello! — But we'll forgive her. We got to watch her sing "I Bust The Windows Out" because of it, so it's all good." Discussing what he hoped to see from Mercedes in the future, Ghosh wrote: "Kind of want to know more about what makes Mercedes tick, maybe get friendly with her parents, have her chase a viable love interest... And if we could see a couple more showstoppers from her, that would be good too. A subdued Mercedes may have been her 'highest note' so far, but seeing that once was plenty. The more opportunities she gets to let her light shine, the better."