Siebel was a German aircraft manufacturer founded in 1937 in Halle an der Saale.

[1] It originated in the Klemm-Flugzeugwerke Halle that had been founded in 1934 as a branch of Leichtflugzeugbau Klemm in Böblingen.

[2] After World War II the company was revived as Siebel Flugzeugwerke ATG (SIAT) in West Germany in 1948, with its headquarters in Munich.

In 1956, its headquarters were moved to Donauwörth and the company became WMD-Siebelwerke ATG (WMD/SIAT) in 1958 in cooperation with Waggon- und Maschinenbau GmbH Donauwörth (WMD).

In 1968 the company was absorbed by Messerschmitt-Bölkow-Blohm after MBB became the major shareholder.