While polygamy is illegal in Sri Lanka, Muslim men take up to four wives. Like most countries that allow for polygamous unions, the husband must notify his first wife prior to taking additional wives. Polyandry is also protected under the law for Muslims and non-Muslims.
Polygamy and polyandry also have a history in the country and were practiced within the royal family till the end of colonial period.
References
Polygamy in Sri Lanka Wikipedia(Text) CC BY-SA