Spartan
Etymology
From Sparta, the ancient Greek city-state whose citizens were raised from childhood for war under a regime of relentless discipline, plain living, and endurance of hardship. Comfort and luxury were treated as weakness. The adjective preserves that ethos, naming any austerity embraced as strength rather than suffered as deprivation.
adjective · /SPAR-tun/
Marked by severe simplicity, austerity, and self-discipline, with no comfort or excess.
What it names
Deliberate bareness as a virtue — use it for a room, a diet, a lifestyle, or a regimen stripped down to the essentials on purpose.
Example
His apartment was spartan: a mattress, one chair, a lamp, and nothing on the walls.
Related idea
Ascetic usually implies giving up pleasure for spiritual or moral reasons; spartan is about lean, disciplined austerity, often for toughness or focus rather than piety.