The Ayutthaya–Lan Na War is a border conflict that takes place between 1441 and 1474.

It starts when the southern kingdom of Ayutthaya invades the northern kingdom of Lan Na in 1441 and continues with periodic breaks until 1474.

Lan Na achieves limited territorial gains but is weakened by internal power struggles and losses sustained during the conflict.

Ayutthaya forms what is now the central and southern parts of modern Thailand while Lan Na approximates northern Thailand.