Apple Intelligence runs its models on your Mac, and those models are downloaded to your disk. Here's roughly how much space that takes, where it shows up, and how to get it back if you don't use it.
Apple says Apple Intelligence needs about 7 GB of available storage on a Mac, and the requirement has grown as features were added. The models download in the background after you turn it on, so the space goes quietly.
Other on-device features — Siri voices, dictation and translation languages — download their own assets too.
The models are system assets, so in System Settings → General → Storage they count toward macOS (or System Data), not toward any app. They're stored in protected system locations, so you can't — and shouldn't — delete them by hand.
If you don't use Apple Intelligence, turn it off in System Settings → Apple Intelligence & Siri. macOS can then remove the downloaded models; the space may take a while to come back. Turning it on again downloads them again.
To see how your disk's space is split overall, scan your startup disk with DiskGarden — and if the macOS category is still large, see why macOS takes up so much space.
DiskGarden is a free disk space analyzer for Mac: it maps every folder by size, so the space hogs stand out. No account, and your files never leave your Mac.