Choice of Master for third-year students: How many choices of master can I do?
It depends on the type of Master you are applying for. If you apply for a non-selective programme (besides dual degrees, master joint and masters offered at the School of Journalism), you have to provide only one choice.
However, if you apply for a programme as subject to an admission committee, you must indicate a second choice that is not.
Be careful, there is an exception: if you are applying to the Sciences Po / École du Louvre partnership at the undergraduate degree, you are not required to choose a master's degree or language, but you must tick the box “Ecole du Louvre partnership, gap year”.