South Yorkshire Police has confirmed that the man is in a serious condition in hospital after the attack in Gleadless Valley last night.
Emergency services were called to Middle Hay Close shortly before 8.30pm yesterday following reports a man had been attacked by three men dressed in dark clothes and wearing balaclavas.
A statement said: “A 21-year-old man had been assaulted, allegedly with a machete, and had received serious injuries to his head.
“He was taken to hospital by ambulance where he remains in a serious but stable condition.
“At this time it is believed that this was a targeted attack and there is no cause for concern for those in the local community.”
Police said enquiries are continuing in the area.
If you saw anything, you’re asked to call 101 quoting incident number 819 of 19 September 2019. You can also pass information to Crimestoppers anonymously on 0800 555111.