South Yorkshire Police said a body was found in the water at Victoria Quays, close to the Hilton Hotel, at around midday.
The body has not yet been identified but is believed to be that of 19-year-old Alex Wilson, who vanished on a night out in Sheffield city centre in the early hours of Sunday.
A South Yorkshire Police spokeswoman said: "Specialist officers searching for missing teenager Alex Wilson have today found a man’s body.
"Extensive searches have been carried out in Sheffield city centre since 19-year-old Alex went missing in the early hours of Sunday.
"At around midday, officers searching the area found the body of a male in the water by Victoria Quays close to the Hilton Hotel.
"He has not yet been formally identified but police believe it to be Alex. His family has been informed and are being supported by specially-trained officers.
"Work continues today to establish the circumstances surrounding his death.
"Police continue to appeal to anyone who may have seen Alex to come forward."
Alex, from the Norwood area of Sheffield, got into a taxi on Carver Street in the early hours of Sunday and got out of it a short time later on Arundel Gate.
CCTV cameras captured him making his way to the train station before heading in the direction of Ponds Forge.