Less common Chinese surnames romanized as Han include: 寒 (han2) and 汉 (simp. han4) or 漢 (trad. han4).
Han (韩) is currently ranked 25th in China in terms of the number of bearers at around 8 million persons.
'姬' (Ji4) is an ancient Chinese surname. It is the surname of the Yellow Emperor and the Zhou ruling family. King Cheng of Zhou's little brother Ji Wan '姬万' (Ji4 Wan4) created the State of Han '韩国' (han2 guo2). When this kingdom was destroyed, Ji Wan was granted the name Han Wuzi '韩武子' (han2 wu3 zi3). Wuzi's descendant Han Jue '韩厥' (han2 jue2) adopts Han as a last name. Han Jue's 7th generation descendant created the State of Han during the Warring States Period. When the state was conquered by Qin in 230 BC, members of the ruling family adopted Han '韩' as their last name.
King Cheng of Zhou's younger brother, Tang Shuyu '唐叔虞' (Tang2 Shu1 Yu2), also known as the founder of the State of Jin, had a son who was named Jin Hou '晋侯' (Jin4 Hou4). Jin Hou's descendant, Bi Wan '毕万' (bi4 wan4), was assigned to Han Yuan. His descendants adopted Han '韩' as their last name.
Non-Han ethnic groups tend to adopt Chinese last names through the process known as sinicization.
During the reforms of Emperor Xiao Wen of Northern Wei, the Xianbei last name 'Dahan', 大汗 (da4 han4) in Chinese, was changed to Han '韩' because the two names sound similar after 'Da' or '大' is dropped.
Manchu clan names Hacihuri '哈思呼哩' (Ha1 Si1 Hu1 Li1), Hangiya '韩佳' (Han2 Jia1), Hanja '罕扎' (Han4 Zha1), Hanyan '翰颜' (Han2 Yan2), and Gilate '吉喇特' (Ji2 La3 Te4) were changed to Han '韩'.
The mythical Yellow Emperor had a son Chang Yi (昌意), who had a son with the given name Han Liu (韩流). Those who claimed to be Han Liu's descendants adopted Han as their last name.