It depends on the conditions.
We believe that monogamy is the ideal in marriage, as reflected in God’s creation of life in pairs of male and female, as mentioned in various Qur’anic verses.
Where polygamy is illegal, then it is illegal for Muslims to marry more than one wife, which is the case in the U.S. and other Western as well as in many Muslim countries.
The Qur’an does, however, allow men to marry more than one wife with the condition that he treat all wives equally, a standard that even the Quran warns is difficult to achieve, clearly implying a preference for monogamy.
The Qur’an declared polygamy permissible 1400 years ago in the context of war, when caring for orphans was a major concern; polygamy in this situation was supposed to assist widowed women with children who otherwise would have been left to fend for themselves in a brutally patriarchal social order.
Polygamy was, of course, not peculiar to the Arabian peninsula; it was widespread in many cultures, including that represented by the Hebrew Bible, where the Patriarchs are all depicted as having multiple wives and Israelite kings had harems numbering in the hundreds.