| Katarzyna Tomicka z Iwna | |
| House-Type: | Szlachta |
| Noble Family: | Tomicki |
| Coa: | Łodzia |
| Father: | Jan Tomicki h. Łodzia |
| Mother: | Barbara Potulicka h. Grzymała |
| Spouse-Type: | Consort |
| Issue: | Mikołaj Radziwiłł Krzysztof Mikołaj "the Thunderbolt" Radziwiłł Barbara Radziwiłł |
| Birth Date: | 1516/1518 |
| Birth Place: | Iwno, near Kostrzyn |
| Death Date: | 1551 |
| Death Place: | Wilno, Grand Duchy of Lithuania |
Katarzyna Tomicka (c.1517 - 1551) was a Polish noblewoman,[1] known as the sister-in-law and opponent of her sister-in-law queen Barbara Radziwiłł.
Katarzyna was born in Iwno, the third daughter of podkomorzy of Kalisz, Jan Tomicki h. Łodzia and sister-aunt of the Court Marshal and Bishop of Kraków, Piotr Tomicki h. Łodzia. She died in Wilno.
Her sons initiated the so-called "Calvinist lineage" of the Radziwiłł family. The male line expired in 1669.
Katarzyna married Mikołaj "Rudy" Radziwiłł around 1542 and had three children: