According to Genesis, God shut the door of Noah's Ark.
Genesis 7:16 says that the people and animals entered the Ark as God had commanded, and then “the LORD shut him in.” The sentence places the closing of the Ark’s entrance under divine action rather than describing Noah or one of his sons securing it.
This detail comes immediately before the Flood narrative intensifies. The family and animals are inside, the entrance is closed, and the waters then rise. In the story’s literary structure, the closing marks the transition from preparation to judgment and protection.
Illustrations often show Noah pulling a large door closed because that is visually straightforward. The biblical text does not say that he did so. It also does not name an angel as the one who closed the door. The specific answer supplied by Genesis is God, expressed in the text as “the LORD.”