Almost 100 people have been charged with drug offences at two Sydney dance parties overnight.

Seven people were charged with supplying ecstasy to patrons attending the Supremacy dance party at Sydney's Olympic Park.

Another 26 people at the Saturday night event were charged with possessing MDMA while three others were busted carrying drugs other than ecstasy, NSW Police said in a statement on Sunday.

"There was a high instance of drug affected and intoxicated people observed during the operation with over 60 people requiring treatment by medical staff," a police spokesperson said, adding one patron was taken to Concord Hospital for a ketamine overdose.

Meanwhile, 62 people were charged with possessing a prohibited drug at the Sydney City Limits music festival held at Centennial Park on Saturday.

One person was taken to Prince of Wales Hospital suffering a suspected overdose.

"Police remain concerned that people continue to risk their health and a criminal record by taking illicit drugs to events like this one and will continue to conduct similar operations at future events," the police spokesperson said.