Combat Sambo (Боевое Самбо), originally from the former Soviet Union, and has been popularised by Khabib Nurmagomedov & Islam Makhachev. Sambo is a hybrid mixture of Kickboxing, Uzbek Kurash & Catch Wrestling systems from the former soviet union such as put into one fighting style.
Khabib Nurmagomedov & Islam Makhachev are the most famous Sambo fighters in the UFC at present