Abstract: A portable collapsible shelter comprises a floor, pairs of corner posts, a horizontal brace extending between and pivotally attached to the corner posts of each pair, and built-in seats. The floor, corner posts, braces, and seats are foldable between respective erected and collapsed modes. In the collapsed mode, each corner post is folded into a stack, with the stacks of each pair thereof being coplanar. The associated brace is initially at the top of the stacks of folded corner posts. The brace folds into a stack located coplanar with and between the stacks of the associated corner posts when the floor is folded to its collapsed mode. The seats fold with the corner posts and lie on the floor when the corner posts are folded to their collapsed mode. Locking devices selectively prevent and enable folding of the floor, corner posts, and braces.