John William Jones, 62, was found on the floor of his house with a stab wound to the chest, local police chief Mohamad Iqbal Ibrahim told AFP.
His British wife, whose identity was not disclosed, has been detained and is suspected of having murdered him following a row, he said.
The pair had lived on Langkawi for the past 11 years, Iqbal said.
“The couple were believed to have engaged in an argument. The wife then took a knife from the kitchen and stabbed her husband in the chest,” he said.
A 30cm knife was found on the floor of the couple’s bedroom covered in blood stains, he said.
Local media reported the victim’s body was discovered early yesterday after neighbours alerted police.
Under current laws, the wife will be sentenced to death by hanging if she is found guilty of murdering her husband. Murder carries a mandatory death sentence in Malaysia.
The government recently pledged to abolish the death penalty for all crimes but lawmakers still have to approve the changes.