The Scottish 19-year-old, who began his career in Celtic's youth ranks, recently impressed on trial for the Magpies and has been awarded a two-year contract with Newcastle.
The Coatbridge-born shot-stopper made his senior debut for East Fife at the tender age of 18 before going on to record 28 competitive appearances for the Methil-based club during the 2021/22 campaign.
"I'm buzzing to be signing for Newcastle United," Smith told nufc.co.uk. "After playing in the lower leagues of Scotland, I couldn't be happier with the opportunity to go and play for a club like Newcastle.
"I was playing part-time at East Fife last season so it's a great opportunity to be full-time with Newcastle. It's an unbelievable chance for me to go and develop my career further so it was a no-brainer for me to join.
"Playing for East Fife's first-team was good experience, especially at a young age, and playing mens' football did me the world of good. I just want to be playing week in week out, especially as a goalkeeper.
"It's the next chapter in my life which I'm looking forward to and really hope to kick on."
Smith becomes the club's fourth summer signing at youth level following the arrival of Irish defender Alex Murphy from Galway United, full-back Jordan Hackett from Tottenham Hotspur and centre-back Charlie McArthur from Kilmarnock.
Photograph courtesy of East Fife F.C.