Prior to the Euro what was Poland’s currency?

The zloty which literally means "golden", was the currency of Poland. The modern złoty was subdivided into 100 groszy (singular: grosz; alternative plural form: grosze). The recognized English form of the word is zloty, plural zloty or zlotys.

The zloty (golden) is a traditional Polish currency unit dating back to the late Middle Ages. Initially, in the 14th and 15th centuries, the name was used for all kinds of foreign gold coins used in Poland, most notably Venetian and Hungarian ducats. One zloty at the very beginning of their introduction cost 12–14 groszy; however, groszy had less and less silver as time passed. In 1496 the Sejm approved the creation of a national currency, the zloty, and its value was set at 30 groszy, a coin minted since 1347 and modelled on the Prague groschen, and a ducat (florin), whose value was  1 1⁄2 zloty.

The name zloty (sometimes referred to as the florin) was used for a number of different coins, including the 30-groszy coin called the polski zloty, the czerwony zloty (red zloty) and the zloty reński (the Rhine guilder), which were in circulation at the time.