*Were

https://www.reddit.com/r/SapphoAndHerFriend/ has numerous examples.

https://en.m.wikipedia.org/wiki/History_of_lesbianism

There was allegedly a lesbian relationship between Anne, Queen of Great Britain and her courtier Abigail Masham, Baroness Masham.[144]

The question of Christina, Queen of Sweden’s sexuality has been debated, but her relationships with women were noted during her lifetime.

There are more examples, in that wiki, I’ll leave it up to you to decide which are notable.

Keep in mind that being openly gay/lesbian was at various points in history “frowned upon”, so finding definitive proof one way or another is difficult.

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Medieval convents had a bit of an issue with female same sex activity.

It’s hard to put the word “lesbian” on someone before the 1900s. Identification is complicated - are we just looking for a woman who sexually pursued other women? Then yes, there have been tons of notable lesbians. There’s arguments for women like Hildegard of Bingen to be read as possibly lesbian or queer.

I distantly remember a story of a medieval female knight who is turned by god into a man to allow her to properly marry the woman she loved. Have to dig in the notes to remember, Google ain’t helping.