Koceila Julien Mammeri (Arabic: كسيلة جوليان معمري; born 23 February 1999) is a badminton player who trained at the Oullins club in France.

[2][3] Born in France, he represents Algeria internationally.

[4] He won gold medals at the 2017, 2019, 2020, 2021 and 2022 African Championships for men's doubles with his partner Youcef Sabri Medel,[5][6] and in 2018 and 2019 for mixed doubles with Linda Mazri, and also in 2021 and 2022 for mixed doubles with Tanina Mammeri.

[7][8] He claimed the mixed doubles gold medals at the 2019 African Games with Mazri and in 2023 with Tanina Mammeri.

[9] Partnered with her sister Tanina Mammeri, the duo competed at the 2024 Summer Olympics.