The 21st Separate Guards Red Banner Omsk-Novobug Order of Bogdan Khmelnitsky Motorized Rifle Brigade, or simply the 21st Guards Motor Rifle Brigade was a formation of the Russian Ground Forces based in Orenburg Oblast.

It was formed on 1 June 2009 from the 27th Guards Motor Rifle Division as a result of the 2008 Russian military reform.

[2] In the spring of 2024, the 27th Guards Motorized Rifle Division was revived and 21st Brigade disbanded.

[9] A Ukrainian Headquarters briefing held on 11 March 2015 noted the 21st Motor Rifle Brigade units are operating near Yenakiieve, Ukraine.

[10] Bodies of soldiers, reportedly from the division, which were killed in the 2022 Russian invasion of Ukraine near Rusaniv [uk] were among six that were to be swapped for two captured Ukrainian soldiers in an exchange in March 2022.