Is my marriage to a woman who has converted to Islam valid if I conceal from her that I am already legally married, or must I inform her of that?

The husband is not obligated to inform his second wife that he is married to another woman, and this does not affect the validity of the marriage if its pillars and conditions are met. Sheikh Ibn Jibreen issued a fatwa stating that a man is not required to inform his wife or her family of this unless he is asked. However, lying is not permissible. If the man lies and claims he is not married, then the wife has the right to annul the contract.