The creator god who separated heaven and earth in Chinese myth is Pangu.
Pangu begins inside a cosmic egg or undifferentiated chaos, often called Hundun. After emerging, he separates yin from yang, with the lighter, clearer substance becoming heaven and the heavier, murkier substance becoming earth. In many versions, he grows between them to keep the two realms apart.
The separation is traditionally said to unfold over 18,000 years. After Pangu dies, parts of his body become features of the natural world: his breath becomes wind, his voice thunder, his eyes the sun and moon, and his body mountains and terrain. Details vary across retellings.
Pangu’s story is influential but comparatively late in the surviving written record. The myth is first associated with third-century texts attributed to Xu Zheng during the Three Kingdoms period. That means Nüwa and other figures belong to older or separate creation traditions; they are not interchangeable with Pangu in this specific heaven-and-earth separation story.