The girls' 100 metre backstroke event at the 2018 Summer Youth Olympics took place on 7 and 8 October at the Natatorium in Buenos Aires, Argentina.

[1] The heats were started on 7 October at 10:48.

[2] The semifinals were started on 7 October at 18:30.

[3] The final was held on 8 October at 19:06.

This swimming-related article is a stub.