Sweet Polly Oliver is an English folk song (Roud #367), dating from at least 1840. It is also known as "Pretty Polly Oliver".

It is one of the best known of a number of folk songs describing woman disguising themselves as men to join the army.

The song is mentioned in Terry Pratchett's Monstrous Regiment, as the song Polly Perks remembered from her childhood, which inspires her to choose "Oliver" as her military name.

Thomas Root wrote a symphonic band arrnagement of Sweet Polly Oliver.

As sweet Polly Oliver lay musing in bed,
A sudden strange fancy came into her head.
"Nor father nor mother shall make me false prove,
I'll 'list as a soldier, and follow my love."
So early next morning she softly arose,
And dressed herself up in her dead brother's clothes.
She cut her hair close, and she stained her face brown,
And went for a soldier to fair London Town.
Then up spoke the sergeant one day at his drill,
"Now who's good for nursing? A captain, he's ill."
"I'm ready," said Polly. To nurse him she's gone,
And finds it's her true love all wasted and wan.
The first week the doctor kept shaking his head,
"No nursing, young fellow, can save him," he said.
But when Polly Oliver had nursed him back to life
He cried, "You have cherished him as if you were his wife".
O then Polly Oliver, she burst into tears
And told the good doctor her hopes and her fears,
And very shortly after, for better or for worse,
The captain took joyfully his pretty soldier nurse.