History: In the nineteenth century, European sailors wore straw hats with flat crowns and brims. As the design was phased out for military wear, it gained popularity in the late 1800s and early 1900s as a men’s formal summer daytime hat (worn with a suit) particularly at sailing events. The name “boater” was adopted as the hat took off in popularity. 
Around the same time, a similar hat for late Victorian era women and children, known as the “sailor” was widely worn. With a larger brim size than its male ‘boater’ counterpart, sailor hats were trimmed with a dark hatband that extended to ribbon streamers trailing down the back. Women’s sailor hat designs often featured flowers around the base of the crown as well.
Difference Between a Boater and a Sailor: Both hats have a completely flat crown and brim. Traditionally, boater hats are made with stiff straw and are trimmed only with a hatband (in solid or striped grosgrain ribbon). The brim size of a traditional boater is modest- noticeably smaller than a the brim on a sailor hat. Historically, sailor hats have wider brims than a boater and were made of all kinds of weights of straw and felt. 
Difference between a Boater and a Matador: They are also the same basic shape- both hats have a flat crown and brim. A Matador crown is visibly taller and the hat often includes a chin strap. The name is confusing as most Spanish matadors actually wear a traditional Iberian “Montera” hat as part of their bullfighting costume, a hat that looks completely different!
Characteristics: A boater has a perfectly round crown and brim, both of which sit horizontally flat.
Royals Associated with this Hat Style: Princess Beatrix of the Netherlands has long been a boater wearer, as has Queen Elizabeth. Princess Beatrice of York has also embraced boaters in recent years.
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Queen Elizabeth on May 16, 2017; Princess Beatrice on June 16, 2016
Princess Beatrice, June 17, 2017; Princess Tsuguko, August 19, 2013
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Queen Elizabeth, March 24, 2016
Princess Beatrice at Ascot, June 18, 2019; The Duchess of York in July 2021
Boaters are seeing an upswing in popularity and I suspect we’ll see them appear on more royal heads- what do you think of this hat style?
Photos from Getty as indicated and Samir Hussein via Getty; The Asahi Shimbun; Mark Cuthbert/UK Press via Getty; Misan Harriman
Royal Hats 
Replying somewhat belatedly to this, and I apologize because this isn’t actually about hats, I was curious to know what uniform the Princess Royal was wearing at the investiture, as I believe she is associated with various military units. Online, I discovered that she has been doing investitures since 2014, always wearing the same uniform (at least as identified by the unique detailing on the sleeve), and always only photographed from the right side or the back. Anyone ever seen any front view photos of Anne doing an investiture or know anything more about the uniform?
(The lack of front view photos anywhere online leads me to believe that the use of personal cameras by those in attendance or cell phones to take photos during the ceremony is likely prohibited.)
Splendid post, HQ. I didn’t know the distinction between a sailor and a boater.
Are the line drawings your own? You don’t list an artist. They are so charming as well as illustrative!
The line drawings are photoshop mashups of public domain images so not my own drawings but my own creations!
21st century line drawings!
Two photos of the future Princess of Wales at Ascot prior to her wedding — two of the earliest times Lady Diana was photographed wearing hats. These were both described as boaters at the time, though I suspect they don’t 100% qualify based on HatQueen’s description in this post. (Possibly more in the “sailor hat” category.)
And here’s Diana in a felt boater: https://i.pinimg.com/736x/21/fb/70/21fb702e55aa59d1cf2d147858c24747–princess-kate-princess-of-wales.jpg
I think of Diana as a fan of boaters, but on closer inspection, as you say, many of her hats are boater-themed, but few are the classic style.
This next royal may not be much of a boater wearer… but she wears them so well, I just had to add these 2 pics. The Princess Royal: https://i.pinimg.com/736x/e6/b7/b1/e6b7b170be643999212513bad67cc717–royal-princess-princess-anna.jpg
http://media.gettyimages.com/photos/her-royal-highness-princess-anne-poses-for-a-21st-birthday-portrait-picture-id594367770
Can a felt hat be considered a boater, even if in the perfect shape? I was under the impression that the term boater necessarily referred only to hats of straw.
Hi Matthew, that’s what I used to think too, until I read HQ’s full description in her post. Seems like the definition has broadened over the years.
I tend to agree with mcncin that the Countess of Wessex’s hat, with its wide brim, would seem more of a picture hat than a boater, even though it has the requisite flat crown. Where does the line come? (If I understand mcncin correctly, I also agree that the two hats that seem to push the boundaries of the boater are the most interesting.)
A very timely post, HQ – lots of interesting info in your article and very timely too.
To me Sophie’s hat, with its shallow crown and oversized brim, is far more a bergere than a boater; and Camilla’s purple felt hat, with its dipped and upturned brim, is also a “hybrid”. But then, it’s the hybrid hats that are often the most interesting :).
Yes, that looks much more like a Bergère to me too. They are still worn as part of traditional costumes in Europe (because those costumes have roots in Rococo fashion). The little maids of honor at Charlene’s wearing are a well-known example.
You raise good points- I too would have described The Countess of Wessex’s Ascot has as a picture/berere hybrid. Interestingly, the milliner, Jane Taylor specifically described the hat as a boater in all the related press releases. As such I changed the description and included it here. Is it a true boater? No. But I think, as you mention, that these variations on specific hat types show how far milliners push boundaries and how, in some cases, hats fall in grey areas between rigid definitions.
Do all four of the Queen’s children now perform investitures?
I have only seen Charles, Anne and William do them.
90 year old Ishbel Sewell
Dame Beryl Grey
one more
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Yvette Twumasi-Ankrah
Katharine Horler
The boater can be a tricky one for anyone to pull off since it’s such a severe shape; it is even trickier for men to pull off without it looking costumey. But even when it was a common hat for men to wear, it is quite hard to find one on a royal head because they often chose a top hat, homburg, bowler, or military hat instead (the fedora was just coming into popularity, which I believe led to the demise of the boater as an everyday hat).
However, here is a photo of two of HM Queen Elizabeth II’s uncles (George, Duke of Kent, and Edward, Prince of Wales) in Canada in 1927:
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And here’s a photo of me wearing the one boater I own:
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Awesome hat and outfit, Jake – thanks!
Love your photo, Jake, and I followed you over there on Instagram. (I am @materialwhirlcollage.) Great hat, and indeed a very dapper look!
Such panache, Jake!
Jake:
1. Great picture of you – very nice ensemble, as are the rest of your pix!
2. It looks like PM Baldwin and his wife just got off a fishing boat, and Countess Lucy got caught up in some of the seaweed, as was mentioned earlier this week on another Royal head.
That’s an interesting pic, Jake. Considering that the men shown are all attending the same event, there is a bewildering variety (and lack) of hat styles! Look at Prime Minister Stanley Baldwin in his country tweed jacket and gardening hat! – but carrying his top hat (couldn’t wait to take it off, I suppose); and I didn’t know that men of that era would wear a morning coat with a boater (then I found this pic, which I would guess is early 1900s): https://78.media.tumblr.com/8b1fb019d5554ff79dfb5454f11c8a00/tumblr_oqp1zk9tng1suvc1vo1_250.jpg
Here is more the sort of jazz outfit I was expecting to see Prince Edward wear with a boater (from the same year 1927): https://i.pinimg.com/736x/1e/1f/da/1e1fda412bdd290d9b6e3530e32d50f9–george-duke-king-george.jpg
Yes, I had never seen morning coats worn with a boater before, so I found that an interesting look at styles from that time. I’m also curious as to what Baldwin is wearing on his head; possibly it’s a panama straw hat that either lost its shape or wasn’t given as much of a shape to begin with, but it’s difficult to tell from this photo. Also odd is that he’s holding onto his top hat while wearing another hat (I somehow failed to notice this when I first saw the photo). The other photo of the two princes you posted looks to be from the same trip to Canada, and yes, this is definitely the type of suite I imagine with a boater. It’s nice to see royal hats from 100 years ago still keeping us on our toes and guessing!
If you go to top of this page, click on “Hat Design Features,” and under Queen Elizabeth, you’ll see ‘Flat Crown, Flat Brimmed Hats” of Angela Kelly. There are TEN examples of boaters found there, some more successful than others. Personally, I find the sharp edge of the crown less attractive on HM than some of the softer, rounded crowns in other designs.
Thanks for the link Jimbo, HQ’s assemblages are so useful!
I agree about the sharp edge lines of the boater being tricky for HM. Angela Kelly seems to favour a crown higher than the classic boater proportions, a variation which can easily look like a sort of cropped top hat. To me, her boaters seem to call for a wide bulky trim, or correspondingly wider (higher) band – which some of them have.
This is a tricky style to get right. Some smaller versions seem too childish. Some unadorned versions seem too severe. Sometimes the crown is too low or too high. I agree with JamesB that Princess Beatrix wears this style well. I personally like the larger brims and fuller trims on Princess Alexandra’s and Countess Sophie’s hats.
They’re not for everyone are they. I really don’t like them on Beatrice, they don’t suit her face shape. I don’t mind them on QEII, some work better than others, but I know they’re not that popular here. On Beatrix however I like them a lot!
But my all time favourite is Sophie’s hat from this year’s Ascot. I suspect that’ll be a fab favourite for many years.