Max Item Level WoW Shadowlands 9.1 is set at 233. Here's everything we know about Max Item levels in Shadowlands.
Max Item Level WoW Shadowlands 9.0: Everything We Know
Currently, the highest item level is 226 for Mythic raiding. This is the cap that Weekly Great Vault Objectives have for both PvP and Mythic Dungeons. The Mythic+ End of Dungeon chests can be up to level 210.
The exception to this are items that can be dropped by Castle Nathria's last two bosses, Stone Legion Generals, and Sire Denathrius. These items can be level 233, a whole seven levels higher than what could be obtained otherwise. These pieces of gear will eventually be phased out in the next patch.
Shadowlands 9.1 is expected to release sometime around February and March 2021.