Karl Troll (November 1, 1865 in Oberwölbling, Lower Austria – December 30, 1954 in Vienna) was an Austrian architect.
Karl Troll was the son of a carpenter from a small village in Lower Austria.
As an excellent student with interest in medieval churches he obtained a scholarship for a study trip to Germany and Italy (about 1892).
Among his independent projects were the city school in Antonsplatz, Vienna 10 (together with Anton Rehak in 1902) and Evangelical Church in Moravská Ostrava (together with Ludwig Faigl in 1905–07).
After the death of Neumann, Karl Troll and Johann Stoppel, another member of the bureau, started an independent office.