You don’t need PS Plus to play Fortnite on PS4 or PS5. Since Fortnite is free-to-play, Sony allows online access without a subscription. However, PS Plus is required if you want to play other online multiplayer games.
Exactly, Fortnite is an exception. You can download and play it completely free on PlayStation without PS Plus. But having PS Plus can give you extra perks like free monthly games and online features for other games.
I’ve tested this myself — no PS Plus needed for Fortnite. Just make sure your game is updated and you’re logged in with your Epic account. Online matches work fine without paying for PS Plus.
A tip: while PS Plus isn’t required, linking your Epic Games account properly ensures you get cross-platform progress and skins. That way you can play Fortnite on PC, Xbox, or mobile with the same account.