The motorway was closed for several hours following reports she was on the bridge near junction 40 just after 7pm on Friday.
The 18-year-old, believed to be local, fell from the bridge and was hit by several vehicles travelling south. She died at the scene.
West Yorkshire Police said:-
"Police are appealing for witnesses following the death of a woman in an incident on the M1 at Ossett.
"Emergency services were called at 7.15pm last night (Friday, 28 December) to reports that a woman had fallen from the roundabout bridge over the M1 at Junction 40 and been hit by a number of vehicles on the southbound carriageway. The woman was confirmed deceased at the scene.
"She has yet to be formally identified but is believed to be an 18-year-old woman from the Wakefield area.
"Police spoke to a number of witnesses at the scene but are keen to speak to anyone else who can assist their ongoing enquiries.
"Anyone who witnessed this incident is asked to call Wakefield District CID via 101, quoting log 1619 of 28/12."