No, guava is not a citrus fruit.
Guava belongs to the genus Psidium, while citrus fruits belong to the genus Citrus. Guavas are more closely related to crepe myrtles than to lemons, limes, oranges, grapefruits, or pomelos. The defining characteristic places guava in a different botanical family than true citrus fruits. Therefore, despite any superficial similarities, guava is definitively not a citrus fruit.
