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:

• Mikołaj Radziwiłł, married Aleksandra Wiśniowiecka h. Korybut and later Zofia Helena Hlebowicz Połońska h. Leliwa
• Krzysztof Mikołaj "the Thunderbolt" Radziwiłł, was married to Katarzyna Sobek z Sulejówka h. Brochowicz, Princess Katarzyna Ostrogska, Katarzyna Tęczyńska h. Tópor and Princess Elizaveta Ostrogska
• NN

• Besala J., Barbara Radziwiłłówna i Zygmunt August, Świat Książki, Warszawa 2007, ISBN 978-83-7391-715-6, s. 138, 142.
• Boniecki A., Poczet rodów w Wielkiém Księstwie Litewskiém w XV i XVI wieku, Warszawa 1887, s. 279 (e-biblioteka Uniwersytetu Warszawskiego).