Bottlenose Dolphins have larger brains humans; Sperm whales have the biggest brains ever.

1st photo shows images of a Bottlenose Dolphin brain, measurements in inches.

John Lilly (1961) "Man And Dolphin".

2nd image of a 1:1 model of a Human brain, scaled with a metal ruler; not that there is some parallax error, which does make the direct measurement from scan inaccurate, but still a noticeable difference (I make the Dolphin brain 6+ inches, while Human at 5+ inches, when measured hands on, though looks 6 inches).