Gregory "Greg" Heffley is an American middle school student and also the main protagonist of the book series Diary of a Wimpy Kid.
- He is a great writer and a good artist. He even managed to make a spot-on replication of the art style of a Pac-Man arcade machine.
- He does a great job dealing with his family, even more so in the films as he managed to get back at Rodrick by tricking Manny to read Rodrick's bikini magazine and getting Rodrick blamed for it and was grounded as a result.
- He is sometimes willing to step up and do the right thing, such as when Rowley forced by the vengeful teenagers to eat the moldy Cheese, and the school later figured out that the Cheese has gone missing, Greg lied to everyone that he threw the Cheese in the trash so he could protect Rowley, even though it resulted in everyone fleeing from him as any physical contact with the Cheese meant that he had the Cheese Touch.
- Greg was especially well portrayed in the films, even more so than his book counterpart.
- Despite being bad with school work, he's pretty smart when it comes to coming up with ideas like getting Rowley to become the school's student council.
- Although Greg has a fair number of unlikeable moments (see "Bad Qualities"), a number of them are rather relatable to the everyday reader, specifically those growing up while in grade school. He comes off as rather unintentionally sympathetic (i.e. the type of protagonist the audience knows is not perfect, but we still root for him nonetheless).
- He can be sociopathic, abusive of Rowley, very vain considering he sees himself being rich and famous one day,
- He can be very dimwitted, lazy, void of responsibility and strangely weird, getting nostalgic about something that reminds him of the womb.
- The exploration of his abusive actions towards Rowley is even worse in Diary of an Awesome Friendly Kid. Presumably because since Greg tends to be an unreliable narrator, his general actions and behavior is presented as more accurate through Rowley since he's more honest than Greg.
- Compared to his movie counterpart, Greg tends to exaggerate his flaws to be viewed as more sympathetic and blames others for his wrongdoings, and it tends to contradict his intended realistic portrayal.
- He is shown to be quite unloyal and disrespectful to those around him. Especially his movie counterpart in the first film, who calls Angie a crazy freak job, and he states that every kid in his school is a bunch of morons.
- In the Wrecking Ball, he conned people into buying useless items, and he celebrated one of his relatives' deaths.