RegionNearest

RegionNearest[reg, p] gives a point in the region that is nearest to point p.

Examples

Nearest point on circle:

RegionNearest[Circle[{0, 0}, 1], {2, 0}]
(* {1, 0} *)

Nearest function:

nf = RegionNearest[Disk[]];
nf[{5, 5}]
(* {1/Sqrt[2], 1/Sqrt[2]} *)

Please visit the official Wolfram Language Reference for more details.