Tier 4

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