The Third Reich Heer(army) and Luftwaffe(airforce) rank of Oberstleutnant is equivalent to that of Lieutenant Colonel in the current day US Army and US Airforce. Wehrmacht students would do well not to mistake it for the similar Oberleutnant, roughly equivalent to a US Army 1st Lieutenant.
The Kriegsmarine equivalent of the Oberstleutnant was called Fregattenkapitän whereas the Waffen-SS equivalent was the SS-Obersturmbannführer.
For a more complete overview
of which ranks existed
, see Wehrmacht ranks
The page that helped me with this writeup is no longer on the internet, but it used to live at www.wehrmacht-association.com/Open_Pages/ranks.htm