|First appearance||The One With Rachel's Sister|
|Last appearance||The One Where Chandler Can't Cry|
|Number of episodes||2|
|Portrayed by||Reese Witherspoon|
|Relatives|| Dr. Leonard Green (father) |
Sandra Green (mother)
Ida Green (paternal grandmother)
Rachel Green (sister)
Amy Green (sister)
Ross Geller (brother-in-law)
Emma Geller-Green (niece)
Ben Geller (step-nephew)
Jill Green is Rachel's younger sister. Jill comes to the apartment looking for Rachel (the only daughter their father is proud of) and attempts to start a new life, as Rachel did. Jill ends up breaking the rules (shopping to excess thanks to her having memorized her father's credit card numbers) and dates Ross to spite Rachel. However, Ross ended the relationship before it could really start after realizing that, if something happened between him and Jill, nothing could ever happen between him and Rachel; although he didn't know whether or not he and Rachel would ever get back together, he didn't want to know that they never could. This caused Jill to leave, as she didn't want to stay around with someone who sabotaged her every move, bitingly asking Ross if he was gay (based on his rejection of her even after she threw herself at him) before departing.
Despite conflicts, Rachel appears to get along with Jill far better than she does with Amy. According to Amy, since her appearance in the show Jill has gained weight around her "butt and face", but this has not been confirmed.
- In The One Where Rachel's Sister Baby-Sits, Amy tells Rachel that Jill has got fat, despite her being lactose intolerant.