I always called them skimmers, although I understand a more common term is boaters.
Made popular by the Oxford and Cambridge set these hats had their heyday in menswear in the 1920s.
I own this cute little navy straw one, sadly I don't have much occasion to wear it.
Women have often donned this pretty little straw hat. Here are a few examples.
1905 summer day dress of pin-striped cotton
1930 Grey Skimmer
1940 Elsa Schiaparelli The Metropolitan Museum of Art
1940s Skimmers (via Tuppence Ha'penny by Charlotte) worn two different ways pushed to the back and perched forward.
Audry in a skimmer
How about a few retro takes?
Charlotte of Tuppence Ha'penny in two pencil skirt looks.
The cool thing about the skimmer? It's back in fashion right now and it can be worn with any look you'd like.
More on the history of skimmers.
Retro Rack is also on facebook where I post additional images and fashion thoughts.