Ziranmen or Zi Ran Men (simplified Chinese: 自然门; traditional Chinese: 自然門; pinyin: zìránmén; Wade–Giles: tzu-jan men; literally
"the ziran natural style"), also known as Natural Boxing, is a Northern internal style of kung fu that is taught in conjunction with Qigong breathing techniques. The style traces its
lineage to Dwarf Xu, who based it on ancient Taoist philosophy. Du Xin Wu, the next bearer of the lineage, served as a bodyguard to Sun Yat-sen, then the provisional president of
the Republic of China. Wu imparted his knowledge of "Natural Boxing" to his eldest son Du Xiu Si and Wan Laisheng, a prominent twentieth century martial artist.