Nicolaas Hubertus Holzken (born December 16, 1983) is a Dutch kickboxer and professional boxer currently signed to ONE Championship, where he competes in the Lightweight division.

[2] Nieky Holzken made his K-1 debut on November 26, 2006, at K-1 World MAX North European Qualification in Stockholm, Sweden.

- Soema na Basi IV: Londt vs. Adegbuyi in Paramaribo, Suriname on August 8, 2013[10] but withdrew for undisclosed reasons.

He was initially scheduled to fight Marc de Bonte in the Glory 13: Tokyo - Welterweight World Championship Tournament semi-finals in Tokyo, Japan on December 21, 2013[11] but his opponent was then changed to Karapet Karapetyan who he had previously fought and beat in February 2012 by decision.

[12] He knocked Karapetyan down in rounds one and two en route to a clear unanimous decision win before facing Joseph Valtellini in the final.

In a back-and-forth fight where both pressed forward, landing powerful but technical punches and kicks, Holzken scored a TKO in the dying seconds of the third and final round to be crowned the inaugural Glory World Welterweight (-77.1 kg/170 lb) Tournament Champion.

[15] The match was rescheduled for Glory 16: Denver in Broomfield, Colorado, US on May 3, 2014[16] but his lingering shoulder injury again forced him out, and he was replaced by Karapet Karapetyan.

[17] On February 6, 2015, Holzken was part of a one-night, four-man welterweight tournament at Glory 19 to determine who would get the next title shot.

[22] It was announced that Nieky Holzken would face Elliot Compton at ONE Championship: Big Bang 2 on December 11, 2020.

[25] Holzken faced John Wayne Parr in a Muay Thai bout at ONE on TNT 3 on April 21, 2021.

[30] As the first fight of his new six-fight contract, Holzken was scheduled to face the one-time ONE Lightweight Kickboxing title challenger Islam Murtazaev at ONE: X on March 26, 2022.