Usually, a model release is mainly needed for commercial use, such as advertising, stock licensing, endorsements, or selling prints through a site. Simply publishing a photo you took is often treated differently, especially if it was made in a public place and is not used in an offensive way or to imply the person endorses something.

That said, the rules vary a lot by country and even by U.S. state, so this is ultimately a legal question. If your gallery site shows ads, offers print sales, or otherwise monetizes the image, a release becomes much more important. You should also check the hosting platform’s terms.

Practical guidance: if it’s just a non-commercial portfolio image, many places allow it, but use common sense and avoid anything embarrassing, defamatory, or suggestive of endorsement. If you want certainty, ask a lawyer in your area. If someone objects, the most likely outcome is that you’d be asked to remove the image.