Is it obligatory for a disbeliever to change his name if he converts to Islam, or is it merely recommended?

If an infidel embraces Islam and their name involves servitude to other than Allah, such as 'Abd al-Masih (servant of the Messiah), 'Abd al-Rasul (servant of the Messenger), or 'Abd al-'Uzza (servant of al-'Uzza), or names exclusive to Allah, such as al-Ahad (The One), al-Samad (The Eternal), al-Jabbar (The Compeller), or "Malik al-Muluk" (King of Kings), and the like, it must be changed. Scholars have agreed on the prohibition of any name that indicates servitude to other than Allah. It is narrated in the Sahihayn (Bukhari and Muslim) that "The most hateful and wicked man to Allah on the Day of Resurrection will be a man who was called Malik al-Muluk (King of Kings)! There is no king except Allah."

If the name is free from the aforementioned issues, but it is one of the names that carry meanings disliked by the soul, such as Harb (war), or Kalb (dog), or names of devils, it is recommended to change it to a better name. The Prophet, peace and blessings be upon him, changed the name 'Asiyah (disobedient) to Jamilah (beautiful).

The Prophet, peace and blessings be upon him, disliked ugly names, whether of individuals, places, tribes, or mountains.

Therefore, if the name involves a violation of creed, it must be changed. If it is something that souls are averse to, it is recommended to change it. Otherwise, there is no harm in keeping it.