What is Mary most famous poem?

There's no single person named "Mary" who is known for a famous poem.

You might be thinking of a specific poet, like:

* Mary Oliver: Her most famous poem is arguably "Don't Hesitate," though many others like "The Journey" and "The Summer Day" are well-loved.

* Mary Shelley: While known for her novel "Frankenstein," Shelley wrote poems as well. Her most famous poem is "Hymn to Intellectual Beauty."

* Mary Howitt: She was a prolific writer, but her best-known poem is "The Spider and the Fly."

To help me figure out who you're referring to, can you provide more information? Perhaps tell me:

* What era is the poem from?

* What is the poem about?

* Do you know any lines from the poem?

This information will help me narrow down the possibilities and find the poem you're looking for.