The Paris CROUS (Centre Régional des Oeuvres Universitaires et Scolaires) runs 44 students residences. 20% of the rooms in these residences are reserved for foreign students who come within the framework of an exchange program or have obtained a scholarship from the Ministry of Foreign Affairs managed by the CROUS. 

The rent for a room or a studio in a CROUS residence is in average of 350 euros per month.

// If you are coming within the framework of an international exchange program (Erasmus or other)

A certain number of rooms in the CROUS students residences is allocated to each Paris university. These rooms are reserved for foreign students who participate in an international exchange program.
To apply for a room in a students residence, you must contact the service of International Relations of your university in Paris. You will be requested to fill out a housing application form (often before 15th June) that can sometimes be downloaded on the university website.

The service of International Relations will inform you later of the decision (allocation of a room or not). But you must know that the welcome capacity is very limited and it is impossible to meet all the demands. 

// If you have a scholarship from the French Government or from a foreign government managed by the CROUS

The International Reception Office of the Paris CROUS has a certain number of rooms available in residences to accommodate foreign scholarship recipients. There again, availabilities are limited.
Apply to the CROUS International Reception Service :
Tel : 01 40 51 37 65 or 01 40 51 37 66 or 01 40 51 37 67

Website : www.crous-paris.fr/article.asp?idcat=AAGA 

// If you are coming on an individual basis and not within the framework of an exchange program or if you don’t have a scholarship

You are not on the priority list to obtain accommodation in a CROUS students’ residence. It is therefore recommended to choose other solutions, like the Cité Internationale Universitaire of Paris or renting a studio from a private owner.