Emergency services were called to reports of an injured child near to a canal bridge over the Shropshire Union Canal at Reapers Walk, Pendeford, just before 4.15pm on Friday, but nothing could be done to save him.
A 16-year-old boy and 46-year-old woman, both from Wolverhampton, have been arrested - the boy on suspicion of murder and the woman on suspicion of assisting an offender.
The family of the dead boy have been informed, police said.
Witnesses reported seeing an air ambulance circling the area and at least two land ambulances at the scene. Police maintained a presence in Pendeford all evening and into Saturday.
A spokesperson for West Midlands Police said: "We’re working hard to understand exactly what happened but at this time we believe the boy was stabbed.
"Our thoughts are with the boy’s family and friends whose lives have been forever changed.
"A cordon has been placed around the scene and we’re speaking to witnesses and fast-tracking a review of CCTV in the area.
"A 46-year-old woman has been arrested on suspicion of assisting an offender. The boy and the woman are both from Wolverhampton and were arrested shortly before 7pm.
"Anyone who saw what happened and has not yet spoken to us should contact us urgently via Live Chat.
"Information can be given anonymously to Crimestoppers on 0800 555 111. Please quote reference number 2838 of May 27.
"Knife crime must stop. Please help us. Visit lifeorknife.west-midlands.police.uk to see how you can help."