Franz Gregor Ignaz Eckstein (Czech: František Řehoř Ignác Eckstein, Polish: Franciszek Grzegorz Ignacy Eckstein) (c. 1689, Židovice – 1741, Lviv) was an Austrian fresco painter of Czech ancestry, who worked in Bohemia, Silesia, and Galicia.
Before 1709, he was a student of . He may also have studied in Rome. His first frescoes were modelled on the complex works of the Italian master, Andrea Pozzo. In addition to frescoes, he painted altarpieces.
In 1711, he was married in Brünn, where he took up residence, although he accepted commissions from many other places, and travelled frequently. From 1727 to 1733, he lived and worked in Krakau. His final two years were spent in Lemberg.
His most important works include frescoes in the of the Minorite monastery in Brünn,, Bernstein Castle, the in Krakau, and the Jesuit church in Lemberg.
The painter and engraver Gottfried Bernhard Göz was one of his best known students.