No, and it's expensive: around €135 in fines. The good news is that Paris has several hundred free public toilets, the famous "sanisettes," spread across the whole city and easy to locate.
It's a punishable offense, not just a taboo
Urinating in public counts as a public-nuisance offense, with a fine generally around €135. The exact legal basis can vary depending on which local text applies, but the amount is in line with other public-space nuisance fines in Paris.
Public toilets have been free since the mid-2000s
The City of Paris made its automated public toilets fully free, with several hundred units across the capital (roughly 435, per the most recent figures published by the city). Most close in the evening, but a growing number stay open late, sometimes until 1am.
An official map helps find them
The City of Paris publishes an online map listing sanisettes and their hours. Third-party apps also exist for spotting the nearest one from a phone, handy in the middle of a day of sightseeing.
Eco-friendly street urinals exist too
Since 2018, Paris has tested public eco-urinals called "Uritrottoirs," installed in some busy evening spots. How widespread they are can vary by neighborhood as the program has evolved.
Cafés aren't required to let you in without ordering
A venue is only legally required to provide toilets for its own paying customers. In practice many cafés will let you use theirs for a quick stop, but it's never guaranteed — better to ask politely than assume it's a right.
Department stores, museums, and train stations are a safe bet
Paris's big department stores, museums, and stations nearly all have accessible toilets, sometimes for a small fee in stations (around one euro) — a reliable option when no sanisette is nearby.
Tips
In an emergency on the street, the quickest move is to look up the nearest sanisette on a map rather than walking into the first café you see, since there's no guarantee you'll be let in. Keep in mind most sanisettes run an automatic cleaning cycle between uses — a short wait is normal.