Chelsea announced on its website on Wednesday (local time) that Ji, who joined the Blues in 2014, will be around for three more seasons.
The 28-year-old midfielder has netted 56 goals in 136 appearances for Chelsea FC Women. Ji helped the club to the FA Women's Super League and FA Women's Cup titles in both 2015 and 2018.
Last season, Ji scored nine times in 30 matches.
"I am always grateful for the opportunities and I am excited to stay with the club," Ji said. "We didn't win any trophies last year, so I want to win everything this year and I want us to be back in the (UEFA Women's) Champions League. This year, we know we need to be more clinical in front of the goal and finish our chances."
Last season, Ji was nominated for the Women's PFA Player of the Year award, a trophy she received in 2015. Ji was also named to the PFA Team of the Year for the fourth time last season.
Internationally, Ji is South Korea's all-time leading scorer with 54 goals in 119 matches.
Chelsea manager Emma Hayes said Ji's decision to stay put sent an important message to the rest of the club.
"Ji is one of the best players in the world. Ji could play for any club in the world but she chose Chelsea and I think that's a big statement from her," Hayes said. "I think her creativity, her ability to run midfield, sets her apart."
Chelsea's 2019-2020 season will kick off at Stamford Bridge against the newly-promoted Tottenham Hotspur Women on Sept. 8. (Yonhap)