SEOUL, South Korea — A longtime friend of Park Geun-hye, the ousted president of South Korea, was sentenced to three years in prison on Friday on charges of abusing her influence to get her daughter illegally enrolled in a prestigious university.

The sentencing of the confidante, Choi Soon-sil, was the first to come in any of the trials resulting from one of the biggest corruption scandals in the country’s history. The scandal provoked months of huge protests that culminated in the parliamentary impeachment of Ms. Park in December and her formal removal from office and arrest on corruption charges in March.

In the sentencing on Friday, Ms. Choi was convicted of conspiring with officials and professors of Ewha Womans University in the capital, Seoul, including its former president, Choi Kyung-hee, to help her daughter, Chung Yoo-ra, win admission there in 2015 despite a lack of qualifications. A recent Education Ministry inquiry revealed that Ms. Chung had been admitted at the expense of candidates with better credentials.

Choi Soon-sil and the professors were also convicted of conspiring to give Ms. Chung good grades, even though she hardly attended classes.