Nouns ending in -eau are usually masculine.
Is chapeau masculine or feminine?
lechapeau
The rule behind it
93.1% of -eau nouns are masculine
In context
J'ai acheté ce chapeau pour 2000 yen.
I bought this hat for 2000 yen.
Il leva son chapeau quand il me vit.
He raised his hat when he saw me.
Elle a brossé le chapeau de son mari.
She brushed her husband's hat.