Lewis, who had attracted interest from Liverpool earlier in the transfer window, has agreed a five-year contract at St James’ Park.
Newcastle said in a statement: “Highly-rated full-back Jamal Lewis has become Newcastle United’s fifth signing of the summer after joining the Magpies from Norwich City.
“The Northern Ireland international has signed a five-year contract at St. James’ Park after earning rave reviews for his performances last season despite the Canaries’ relegation from the Premier League.”
The 22-year-old impressed in 34 appearances last season despite Norwich failing to beat the drop in their first season back in the top flight.
Newcastle boss Steve Bruce added: “Jamal is a very exciting prospect. I watched him flourish in the Championship two years ago and he made a real fist of it in the Premier League last season.”
Lewis is Newcastle’s third signing in two days after England striker Callum Wilson and Scotland winger Ryan Fraser joined on Monday.