A college at the University of Cambridge is to start accepting both men and women aged 18 and over.
Lucy Cavendish is one of three women's colleges at the university and only admits those over the age of 21.
It was set up in 1965 to help increase female enrolment but will change its admission rules from October 2021.
The college said it would allow it to "widen participation" by making more places available for students from under-represented backgrounds.
Its president, Prof Dame Madeleine Atkins, said: "Women of all ages now have access to all Cambridge colleges as undergraduates, graduates and fellows.
"The demographics of participation in higher education have also changed, and there are now relatively fewer women unable to go to university at 18 or 19, regardless of their background."
However, some former students said on Twitter they were disappointed with the move, with one calling it "a very sad day".
One wrote: "Nobody in their right mind would argue with outreach activities but now Lucy will be like every other Oxbridge College, instead of the amazing, unique place it was."
Another said: "I wouldn't have dared compete with 'normal age students' - I didn't have the confidence - but I did dare to apply when I thought the students were all mature women."
A spokesperson for Lucy Cavendish College said it consulted more than 2,500 people, including current students, staff, alumnae and donors, and found "the vast majority" supported the college "going mixed".
They said it would still be able to provide women-only accommodation and rooms in quieter areas for mature students, if they requested it.
The college, which offers courses including medicine, English and law, counts actress Dame Judi Dench and broadcaster Sandi Toksvig among its honorary fellows.