The Royal Spring (Zdrój Królewski) is a well located in Romuald Traugutt Park on Zakroczymska Street in Warsaw.

In the 18th century it was very popular with residents of the Warsaw New Town as well as travellers, although the drinking water had to be paid for.

It used the characteristic ogive-style arches and the interior walls and exterior were covered with typical red brick.

On the front side of the building is a plaque in Latin: "STANISLAUS AUGUSTUS PROSPICIENDO PUBLICAE SALUBRITATI Hunca FONTANA RESTAURARI JUSSIT.

ANNO MDCCLXXI" (Stanislaus Augustus in the interests of public health commanded the source to be restored to order in the year 1771).