On "Gilmore Girls," Rory's first serious boyfriend is Dean Forester, whom she meets at Stars Hollow High in season one.
Dean is a new student who has moved to Stars Hollow from Chicago. Rory notices him at school, and their early connection becomes one of the first major romantic storylines in the series. Their relationship also briefly makes Rory question whether she wants to leave Stars Hollow High for Chilton.
Dean and Rory date through much of the first two seasons. On their three-month anniversary, Dean tells Rory that he loves her; when she cannot immediately say it back, he breaks up with her. They later reconcile, but their relationship becomes strained as Rory develops feelings for Jess Mariano.
Tristan, Jess, and Logan are common alternatives, but they enter Rory's romantic life at different points. Tristan is a classmate with a crush on her, Jess becomes a later boyfriend, and Logan does not appear until Rory's Yale years. Dean is therefore the canonical answer for Rory's first serious relationship.