The woman, who is in her 30s, was approached by a man in Cromford Road, Langley Mill, sometime between 1am and 2am on Sunday.
A Derbyshire Constabulary spokesperson said: “He tried to engage her in conversation before assaulting her.
“She has described him as white with dark hair and aged in his late 20s. He is around 6ft tall and of medium build. He wore a black coat.
“We want to hear from witnesses or anyone who was driving in the area at the time who may have recorded dashcam footage.”
People can contact the force via the following methods, quoting reference 220*31290.
Facebook – send a private message to /DerbyshireConstabulary
Twitter – direct message the force’s contact centre on @DerPolContact
Website – complete the contact form at www.derbyshire.police.uk/ContactUs
Phone – call 101
You can also anonymously contact Crimestoppers on 0800 555 111.