1924, Desio received the honorary title of city with a royal decree.

In 1944 the opera singer Giuseppina Finzi-Magrini was killed in an American air raid on Desio.The town is known for being the birthplace of Achille Ratti, later Pope Pius XI (born 1857, elected Pope 1922, died 1939), information which the road sign on Desio's border recalls. In the centre, more precisely in Via Pio XI 4, tourists and citizens can visit the Pope's house every Sunday.