Hong Meng, Hung Meng, or Hung Mung (simplified Chinese: 鸿蒙; traditional Chinese: 鴻蒙; pinyin: Hóngméng; Wade–Giles: Hung-meng), literally the Vast Mist, is a character in the Daoist text Zhuangzi and a metaphor for the "primordial world, primeval chaos" in Chinese creation myths. Like many Zhuangist names, Hong Meng is a word play, translated as "Mists-of-Chaos", "Vast Obscurity", "Big Concealment", "Vital Principle", "Natural Energy" and "Big Goose Dummy".

Hong Meng compounds hong 鴻 "wild goose, swan; vast, great" and meng 蒙 "covered; ignorant (esp. in childhood), untutored; encounter, receive; (Yijing) Hexagram 4". The (ca. 111 CE) Hanshu biography of the Daoist author Yang Xiong writes Hong Meng as 鴻濛, with the variant Chinese character meng 濛 "mist, drizzling rain" (sharing the 氵 "water radical in hong 鴻). In Modern Standard Chinese usage, hongmeng 鴻蒙 is a literary metonym meaning "primordial world; primeval atmosphere of nature" before Pangu created the world.

Hong Meng first appears in the (ca. 3rd century BCE) "Outer Chapters" of Zhuangzi (chapter 11, Zài Yòu 在宥) paired with Yun Jiang (simplified Chinese: 云将; traditional Chinese: 雲將; pinyin: Yúnjiàng; Wade–Giles: Yün-chiang). This character name combines yun 雲 "cloud, clouds" and jiang 將 "military commander, general officer; (Chinese chess) general corresponding to (chess) king". English translators of the Zhuangzi have rendered Yun Jiang and Hong Meng as:

Yun Jiang meets Hong Meng twice in three years, both times when wandering or traveling eastward. First, Yun Jiang was passing the fuyao zhi zhi 扶搖之枝 "branch(es) of a whirlwind". Watson (1968:121) notes fuyao 扶搖 "whirlwind; typhoon" appears in Zhuangzi chapter 1, but suggests this context is an error for fusang 扶桑 "a huge mythical tree in the eastern sea from whose branches the sun rises." Both interpretations are possible, compare "an offshoot of a whirlwind" (tr. Mair 1994:97) and "the branches of the sacred wood" (tr. Wang 1999:163). Second, they meet when Yun Jiang was passing the Song zhi ye 宋之野 "wilds of Song" (present day Henan), and respectfully addresses Hong Meng as tian 天 "heaven; heavenly master".

Cloud Chief was traveling east and had passed the branches of the Fu-yao when he suddenly came upon Big Concealment. Big Concealment at the moment was amusing himself by slapping his thighs and hopping around like a sparrow. When Cloud Chief saw this, he stopped in bewilderment, stood dead still in his tracks, and said, "Old gentleman, who are you? What is this you're doing?"

Big Concealment, without interrupting his thigh-slapping and sparrow-hopping, replied to Cloud Chief, "Amusing myself."

"I would like to ask a question," said Cloud Chief.

"Oh dear!" said Big Concealment, for the first time raising his head and looking at Cloud Chief.