Seventeen-year-old Toulouse keeper Alban Lafont produced an inspired display as French champions Paris St-Germain suffered another defeat.
Yann Bodiger scored from the penalty spot after ex-Toulouse defender Serge Aurier was sent off for a second yellow following a foul on Ola Toivonen.
Lafont denied Edinson Cavani three times before Jimmy Durmaz made it 2-0.
PSG have now lost two of their first seven league games – as many as they lost in the whole of last season.
In contrast, Toulouse moved level on points with leaders Nice, who are away to struggling Nancy on Sunday.
PSG boss Unai Emery, who took over from Laurent Blanc in the summer, will hope to see an improvement when his side travel to Bulgaria to face Ludogorets Razgrad in the Champions League next Wednesday.