Quintus Hortensius was a plebeian appointed to the office of dictator of Rome in the year 287 BC.
When the people, pressed by their patrician creditors, "seceded" to the Janiculum, he was commissioned to put an end to the strife. He passed a law (known as the Lex Hortensia) whereby the resolutions of the multitude (plebiscita) were made binding on all the citizens, without the approval of the Senate being necessary. This was not a mere re-enactment of previous laws. Another law, passed about the same time, which declared the nundinae (market days) to be dies fasti (days on which legal business might be transacted), is also attributed to him. He is said to have died while still in office, thus making him (if true) one of two formal dictators to die in office in history, with the other being Julius Caesar.