I am a wide US 8.5 M. I bought a size 9 and it's a terrific fit. They are a bit roomy around the ankles and mid calf (as expected). But yeah, someone in previous comments mentioned rubbing of the ankles...I only experience that when I'm wearing ankle socks, or no socks at all XD. Con: If you are walking with an umbrella, water will drip inside your shoe because of how wide the opening of the shoe is. Pro: These are super light! Like, crazy light. They're easy to slip these off and on. I think these would be PERFECT for the summer.
OVERALL: I don't regret my purchase! I think for my next purchase, I'll buy a pair that closes around my calf^^