© REUTERSA French police officer stands inside a secure area following the knife attack on Saturday.
Paris police said officers quickly detained the attacker who used a sharp weapon in the assault at around 8 a.m.
One of the people injured was in a serious condition; the other two were more lightly hurt.
Police had no other immediate details.
Posting on social media, Interior Minister Gerald Darmanin described the attack as an "unbearable act" and thanked those who detained the assailant.
Security in Paris is being ramped up as it prepares to welcome 10,500 Olympians and millions of visitors for the first Olympic Games in a century in the French capital.
The Games are to open with a massive open-air ceremony along the River Seine on July 26, a major security challenge in the city that has been repeatedly hit by terror attacks, most notably in 2015.
Most recently, a man targeted passersby near the Eiffel Tower in December, killing a German tourist with a knife and injuring two others.
The Gare de Lyon is one of the busiest train stations in Paris. It is a hub both for high-speed trains that link the capital to other cities and for commuter trains that serve the suburbs and towns in the Paris region.
Reader Comments
But still, indicative of a very serious problem.
They "push" the parked cars forth and back, to fit in a parking space. That doesn't work too well on sloped roads, though ...
And where I saw the remains of this conflict - like street barricades, armoured police cars, and castle-like police stations. And I heard of the deep devide between the indigenous Irish population (often deceptively called "catholics") and the English/Scottish immigrants, usually called "protestants".