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Boys' Trunk Underwear

Big adventures start with a good pair of undies. From playground missions to couch forts, Knobby’s boys’ trunks bring bold prints, favourite colours and plenty of personality to their first layer.

Explore BottleBlend® Performance and soft, smooth TENCEL™ Luxe options in designs they’ll be excited to pick themselves. Choose a favourite pair or stock up with a pack, then check the size guide for their fit. Less boring in the drawer. More fun getting dressed.

Knobby Boys' Trunks: Built for All-Day Play

Built for all-day play, epic energy and zero ride-up. Boys' Trunks are soft, breathable and tough enough to keep up with whatever the day throws at them. Lined with breathable bamboo for next-level softness, they stay put from the skatepark to the sofa, with no ride-up and no distractions - comfy enough that he will forget he is wearing them, which is the entire goal.

Buy Boys' Underwear Online from Knobby

Knobby's boys' underwear is designed in Australia and printed in artwork kids pick out themselves, which is a surprisingly effective way to get undies into the wash rather than under the bed. The trunk cut keeps everything in place for sport and school, and the bamboo lining keeps it soft. Use the size guide on the product page to get the fit right, or join the Undie Club for a new design each month with skip and cancel up to you.

FAQs

Will these ride up during sport?

No - the trunk cut is chosen for exactly that reason. The longer leg holds its place through running, jumping and skating, so there is nothing to tug at mid-game.

What are Knobby's boys' trunks lined with?

Breathable bamboo, which is soft against skin and handles a hot day better than most. It is the same thinking behind the rest of the kids' range.

How do I choose the right size?

Go by the measurements in the size guide on the product page rather than age alone - kids run to their own scale, and the guide will get you closer than a number on a label.

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© KNOBBY AU 2026

At Knobby, we’re proud to work on the Country of the Kabi Kabi (Gubbi Gubbi) People in Chevallum. We honour their deep connection to this land, its waters and community, and pay our respects to Elders past, present and emerging.