Looking strictly at AC

Better than:

+2 Studded Leather (AC 14 + Dex), with Light Armor Proficiency
Bracers of Defense, on Monks or Barbs with Wis or Con 14 or higher respectively, or on those with Mage Armor or other AC boosting effects
Bonespike Boots, same as the above, especially if paired.
Vest of Soul Rejuvenation, same as the above.
Robe of the Weave, same as the above. Lots of other robes and clothing provide +1, which is likely equal to but not better than other than specifically for Monks and Barbs, but from a strictly AC standpoint it’s worse than the listed options.
Armour of Moonbasking, on Druids who spend most of their time wild shaped
Helldusk Armor, with Dex less than 24
Bhaalist Armor, it’s strictly better
Elegant Studded Leather, same deal, strictly better


+2 Half Plate (AC 17 + Dex up to 2)
All of the non-armor options above, but with higher ability score requirements or more pieces needed.
Armour of Agility, with Dex scores of 16 or higher (18 if for some reason comparing with someone who has Medium Armor Master, or MAM)
Sharpened Snare Curiass, with Dex scores of 22 or higher (24 with MAM)
Unwanted Masterwork Scalemail, with Dex scores of 18 or higher (20 or higher with MAM)
Yuan-ti scalemail, with Dex scores of 20 or higher (22 with MAM)
Dark Justicar half plate, it’s strictly better
Helldusk Armor, better even with MAM.

+2 Full Plate (AC 20, no Dex bonus)
All of the Dex enabling options above, but using the values for MAM.
All of the non-armor options above that, but with potentially even higher stat requirements and / or more pieces. For example a Barb with +1 from their boots, +2 from clothes, 23 Con and 18 Dex will end up with an AC of 23, while having 2 hands free for great weapons)
Helldusk Armor, better in every way including AC
Armour of Persistence, strictly better

+1 shield (AC +3)
Adamantine Shield, after a miss for the rest of that turn and next
Viconia’s walking fortress, strictly better

That’s the list! Let me know if I missed anything or got anything wrong. Obviously this list is missing much of the best Armor of the game, stuff like Ketheric’s Shield and Adamantine Armor and Armour of Landfall so forth have benefits that far outweigh strict AC bonuses, but the point of this list is specifically to have the highest AC possible, not the best possible characters.