Generally not required for stays up to three months. Some nationalities require a Schengen visa.
Visitors entering Warsaw, Poland are bounded by the Schengen Agreement, in which Poland is a part of. For citizens coming from Schengen-member countries, no visa is required to enter Warsaw, but national ID must be ready to show at all times. Three months (90 days) is the allowable stay for tourists only.
The Schengen area consists of Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, and Sweden.
Requirements of Tourist Visa
1. Passport (6 months valid after departing Poland)
2. Completed application form
3. Confirmation of travel itinerary including hotel accommodation, or letter from personal acquaintance as host
4. One passport-size photo
5. Proof of payment of visa fee
6. Sufficient funding may be inspected for duration of stay