Newcastle have agreed a deal with Lille for the Netherlands Under-21s defender Sven Botman.
Landing the centre-back for a fee believed to be about £30m means Howe has recruited right across his defence since taking charge last November.
In January he signed England full-back Kieran Trippier and Brighton centre-back Dan Burn.
Left-back Matt Targett also arrived on loan from Aston Villa, with the move subsequently made permanent.
In April, Howe said it would not be the "revolution that everyone thinks it will be" at the club this summer.
A Saudi Arabian-backed takeover of the Magpies in October 2021 made them one of the richest clubs in the world.