Hall, 21, joined Albion from Motherwell in June, 2016, and has made 11 appearances for the Seagulls in the Premier League 2 this season.
He joins Kevin Nolan's Magpies side, who are pushing for promotion and sit third in the League Two table.
Brighton under-23 manager Simon Rusk said: “This is a great opportunity for Ben to gain experience in a first-team environment, as Notts County challenge at the top end of the league table.
“He’s been a regular in the heart of defence so far this season, and his form has rightly attracted interest from outside the club.
“It’s a fresh and exciting challenge for Ben and we wish him the best for the remainder of the season.”
In total, Hall has made 29 appearances for the Seagulls in the Premier League 2 since joining the club, as well as three games in the Checkatrade Trophy.
He also made 18 appearances for Motherwell in the Scottish Premier League during the 2015/16 season - after progressing out of the club’s youth ranks.