A lawn aerator is a garden tool designed to create holes in the soil in order to help lawn grasses grow. In compacted lawns, aeration improves soil drainage and encourages worms, microfauna and microflora which require oxygen.

Lawn aeration constitutes three things: controlling lawn thatch, and reducing soil compaction, making grass roots multiply. Aerating causes the roots to divide or sever apart, which rarely happens naturally. Severing the roots causes them to multiply so the blades of grass multiply keeping the lawn thick and deeply rooted as the holes become engorged with roots.

Soil compaction makes it difficult for grass to develop long roots and disturbs both natural rainwater and artificial irrigation

Lawn thatch is a layer of dead organic tissue that can protect the lawn by moderating temperature and reducing evaporation when it is a reasonable thickness, but too much thatch can limit soil oxygenation and reduce watering effectiveness.