Polanie, Mazowszanie, Wiślanie, Pomorzanie, Ślężanie and many smaller tribes.
Just for comparision... Sarmatian tribes:
NOTE: Have in mind that all first chronicles were written by Greek and Roman authors. So, first written data about Proto Slavs went thru Greek/Latin transcription. Still, we can notice names which are obviously Slavic.
This can be interesting considering that modern science (on the base of old data and newest scientific results) established connection between ancestors of modern Slavic nations (with that Polish too), old Sarmatians, Scythians, ancient Aryans, etc.
See on the same link
Geography of Ptolemy, which includes the entire Balto-Slavic territory in Sarmatia, and on the other that this same region was Scythia. By "Sarmatia", Jordanes means only the Aryan territory. The Sarmatians therefore did come from the Scythians.
"As Goths advanced near to the Euxine (Black Sea) they encountered a purer race of Sarmatians, the Iazyges, the Alani and the Roxolani." Sarmatian tribes were no doubt Slavic.Jordanes gave the history of interaction between the Sclaveni and the Goths as they moved from Scandinavia circa 200 AD. "Sarmatian tribes were distinguished by Sclavonic language."Source:
gog & magog
The ancestors of the Slavs are believed to have included the Sarmatians and Scythians. Moving west from central Asia, they settled in eastern and southeastern Europe during the 2nd and 3rd millennia BC.Source:
Using the decoded Scithian-Sarmatian-Meotian calendar, one can decode the records of this Western Slavonic calendar.Source:
THE INTERPRETATION OF THE WESTERN SLAVONIC INSCRIPTIONS
by Sergei V. Rjabchikov, Krasnodar, RUSSIA
THE SCYTHIANS, SARMATIANS, MEOTIANS, RUSSIANS AND CIRCASSIANS: INTERPRETATION OF THE ANCIENT CULTURES
by Sergei V. Rjabchikov
Tsar derives from a Roman name, Caesar.