Middle Polish (Polish: język średniopolski) is the period in the history of the Polish language between the 16th and 18th centuries. It evolved from Old Polish, and gave rise to Modern Polish.

Many various orthographies were proposed to standardize Polish orthography, including Stanisław Zaborowski's in 1514, Jan Seklucjan's in 1549, Stanisław Murzynowski's in 1551, and Onufry Kopczyński's grammars of 1778 and 1785, all with varying degrees of success.

Middle Polish's phonology differs from both Old Polish's and Modern Polish's, mainly in the vowels, but also somewhat in the consonants.

The consonant system of Middle Polish differs little from that of Old Polish.

The clusters ir/irz/yr/yrz lowered to ér/érz and ultimately to er/erz.

Similarly, the clusters il/ił/yl/ył sporadically and non-permanently lowered to el/eł.

There was also a tendency for prenasal raising.

Or, conversely, sometimes vowels lowered.