Without an explanation from you beforehand? Take that to the HR

Double whammy !!

Go get a way better job now and she will try to get you back. And then you can say no and reject her AND have more money!

Geez, is there any way you could explain it to your boss? I hate when people jump into conclusions like that. And what the f is wrong with your girlfriend? I understand there's never a good time to break up, but during work?? Looks to me like she's scared of what your reaction would be so she did it in the one place where you're supposed to not show your emotions. Breaking up should be a private event between two people. Do it in a private place, for Pete's sake.. Now that I'm done with my rant, Stay strong OP!

I don't know what kind of work you do, OP, but if it's retail, your (ex) girlfriend could've easily been a customer as well. Your (ex) boss is a jackass.

OP is French, he should take that to "les Prud'hommes" (French labour court), this might be a case of wrongful termination.

That's just plain old unfair on both accounts mate, sorry it happened.

After a single instance without any warning? Doubt it. Unless you don't have rights where you live.

Be thankful that both your girlfriend and employer have the "ex" prefix.

Sorry OP, your ex is a total a-hole. Who breaks up with someone while they are at work?