As is suggested by its title the main purpose of this study is a presentation, analysis and evaluation of al-Ghazâlî's ideas on justice and social justice. However, in the meantime we shall have an opportunity to shed some light on an aspect of his intellectual legacy that has remained almost unnoticed: prioritization of what is social, or giving priority to what is social in human behaviour, and in its religious, legal and moral evaluation. This can very briefly be summarised as considering transitive virtues more valuable or praiseworthy than the intransitive ones, and considering transitive vices more vicious or blameworthy than the intransitive ones. We shall try also to put two of al-Ghazâlî's significant approaches to religion, law and ethics in the perspective of social justice, or vice versa. One of these is his remarkable but not duly and properly appreciated approach to fardh1 kifâya. The other is his well-known approach to Maqâsid al-Sharî'a and Masâlih. What is important about them here is that they are going to be treated as references for an idea of social responsibility or collective obligation/duty.