ナイトの鎧 / ナイトのよろい [knight no yoroi] or 'knight's armor' in Japanese.
Final Fantasy I
Stats: DEF +34, EVA -33
Equip: ?
Buy: 36,000 gil (sell: ? gil)
Shop: Melmond
Description: Armor crafted from steel plates
Final Fantasy II
Stats: DEF +22, EVA -26%, MDEF +5%
Equip: all
Obtain: ?
Description: Armor given only to knights
Final Fantasy III

Stats: DEF 25, MDEF 7, weight 1
Use: FRE, ONK, KNT
Treasure: Dwarven Hollows
Type: Body
Other: As 'Knight Armor'
Final Fantasy IV
Stats: DEF 11, MDEF 3, EVA 0, MEVA 1, MND +3
Equip: Cecil
Buy: 8,000 gil (sell: 4,000 gil)
Shop: Mysidia
Pictlogica

Stats (lv1): DEF +30
Buy: - (sell: ? gil)
Obtain: event quests Master Challenge, Master Trial
Type: Accessory, Rarity: ★★★★, Element: -
Record Keeper

Knight Armor (I)
Stats: DEF +53, MDEF +18, EVA 102 (lv1), ? (lv5), ? (lv10), ? (lv15), ? (lv20), DEF +99, MDEF +37, EVA 102 (lv25)
Max Level: lv15 (initial), lv20 (first evolve), lv25 (second evolve)
Type: Armor, Rarity: ★★★★

Knight Armor (III)
Stats: DEF +25, MDEF +11, EVA 99 (lv1), ? (lv5), ? (lv10), ? (lv15), DEF +61, MDEF +26, EVA 99 (lv20)
Max Level: lv10 (initial), lv15 (first evolve), lv20 (second evolve)
Type: Armor, Rarity: ★★★
Category: Equipment