A big ol' Pseudoinonotus dryadeus aka "oak bracket". These fruit bodies can overwinter and last multiple years! This one was about 2ft across
This is a sign of a dying tree, btw: https://www.davey.com/insect-disease-resource-center/oak-bracket/
This is a sign of a dying tree, btw: https://www.davey.com/insect-disease-resource-center/oak-bracket/