Bobby, son of Magpies legend Lee, had been on the books at the club’s Little Benton HQ since the age of 12.
The central midfielder became the club’s youngest-ever player to appear for the under-18s at the age of 14 years and 206 days. He has also represented England at youth level, most recently under-16s.
Clark’s rise at Newcastle and on the national stage did not gone unnoticed, previously attracting interest from the likes of Spurs, Chelsea, both Manchester clubs City and United and Bayern Munich.
He trialled at Liverpool during the summer and now completes his switch after a fee was agreed with Newcastle.
Clark was offered a scholarship deal by the club but a move to Merseyside proved too hard to turn down.
His departure is a massive blow for United as Clark is recognised as one of the country’s brightest talents at his age level.
A Liverpool statement read: “Liverpool FC have completed the signing of Bobby Clark from Newcastle United.
“The 16-year-old joins the Reds' Academy set-up after his switch from the Tyneside club was finalised on Thursday.
“Clark operated as an attack-minded midfielder for Newcastle's youth sides and has represented England at U16 level.”