Tier 4 or Tier four may refer to:
Tier 4 COVID restrictions in England under The Health Protection (Coronavirus, Restrictions) (All Tiers) (England) Regulations 2020, the highest level Level 4 COVID restrictions, in COVID-19 pandemic in Scotland Tier-4 COVID restrictions, in COVID-19 pandemic in Wales Tier IV, a data center standard Tier 4 in United States vehicle emission standards
See also Multitier architecture WTA Tier IV tournaments, Women's Tennis Association tennis second-level tournaments Tier 1 (disambiguation) Tier 2 (disambiguation) Tier 3 (disambiguation) Tirefour Castle, in Scotland