Herbert Nitsch (born 20 April 1970) is an Austrian freediver, the current freediving world record champion, and "the deepest man on earth" having dived to a depth of 253.2 metres (831 feet).

Nitsch has held 33 world records across eight freediving disciplines recognised by AIDA International and one in the traditional Greek discipline of Skandalopetra.

During his career, Nitsch has held 32 world records across eight AIDA-recognised disciplines: Dynamic Apnea, Dynamic apnea without fins, Static Apnea, Constant Weight, Constant Weight without Fins, Free Immersion, Variable Weight, and No-Limits. Currently AIDA is no longer involved in No-Limits events.

Nitsch's first Dynamic Apnea record made in January of 2001 was also the first world record with a monofin. Prior to that, bi-fins (stereo fins) were used. His last Dynamic Apnea record of 183 m (600 ft) set in 2002, was bested by Tom Sietas.

During Nitsch's first Dynamic without Fins record of 131 m (430 ft), he introduced the neckweight (a weighted thick necklace, which he made by filling a bicycle innertube with lead pallets). The neckweight allowed him to swim more horizontally and hydrodynamically underwater compared to a weight belt around the waist. Tom Sietas beat Nitsch's last 2001 distance of 134 m (440 ft).

Nitsch also held the world record in the Constant Weight event, which is considered by many to be the classic free-diving discipline: the diver descends next to a line, not using the line and unaided by a sled, and must maintain a constant weight, meaning that no weight can be dropped for the return to the surface.

Nitsch exceeded the then world record depth in 2006 when he dived to a depth of 110 m (361 ft), but failure to complete the strict surfacing protocols within the allotted time meant that the dive was disqualified. ^{[citation needed]}

In Hurghada, Egypt, in December 2006, he set a Constant Weight world record dive of 111 m (364 ft), exceeding Guillaume Néry's previous record by 2 m.