Hollow Knight has 5 base masks , and you can raise that to 9 total masks by collecting all mask shards.

Quick Scoop

  • Base health: 5 masks.
  • Max permanent masks from shards: 9 total.
  • Extra temporary/lifeblood masks can push the number higher in certain setups, but the standard permanent cap is 9.

Extra note

Some sources mention higher totals when including charms and temporary lifeblood effects, but those are not your normal permanent masks.

TL;DR: 9 masks total is the usual answer for Hollow Knight.