Phommathat

{{more citations needed|date=November 2011}}

{{Infobox royalty

| name =Phommathat
{{lang|lo|ພະຍາພົມມະທັດ}}

| title =King of Lan Xang

| image =

| caption =

| succession ={{hlist |Monarchs of Lan Xang}}

| reign =1428–1429

| coronation =1428

| predecessor =Lan Kham Deng

| successor =Yukhon

| spouse =

| issue ={{unbulleted list}}

Prince Kay Buna Ban

| dynasty =Khun Lo

| father =Lan Kham Deng

| mother =Keo Poum Fa

| religion =Therevada Buddhism

| birth_date =

| birth_place =Muang Sua, Lan Xang

| death_date =1428

| death_place =Muang Sua, Lan Xang

| date of burial =

| place of burial =

| regnal name = Samdach Brhat-Anya Chao Brahma-kumara Bhumadaraja

|}}

Phommathat was the fourth king of Lan Xang (Laos) (ruled 1428–1429). He was Lan Kham Deng's oldest son. He was king for only 10 months. He was assassinated by Nang Keo Phimpha. He was succeeded by Yukhon.{{cn|date=August 2020}}