The article tries to give a general technical and tactical account of the inland fleet warships of the Polish Navy in the interwar period (1918-1939). Ever since 1923 such warships were designed and produced only in Poland. The warships that were built, as well as the blueprints for those that were never actually completed, provide a good idea of the forms and structural solutions prevalent in warship building of that period. The power units used exclusively all kinds of internal combustion engines (petrol engines, Diesel engines, semi-Diesel engines), which worked on various fuels, including special mixes of liquid fuels; the propellers used included propellers operating in airless tunnels, Hotchkiss internal cone propellers (hydro-jet propulsion) and paddle wheels, as well as - in an experimental phase - cycloidal Voith-Schneider propellers, all kinds of hydro-pulsation propellers, Kort nozzle propellers and worm drive propellers for craft used in marshes. The armament used by the warships consisted mainly of guns and howitzers of the 37-195 mm calibre range in armoured turrets as well as heavy and later also large-calibre machine guns mounted on armoured turrets or on turning bases with shields, tarcze. The weapons used had a fairly wide firing range, which usually combined into a joint system of circular firing range. Typologically the craft included monitors, gunboats, heavy and light armed motorboats, including fast river patrolboats, report motorboats and hydroplanes, as well as river minelayers and minesweepers; work was also being conducted on such new types of craft as mortarboats, landing craft, aircraft transport boats, and anti-aircraft division ships, but due to the outbreak of the Second World War, their construction had to be abandoned. The design standards of the Polish inland fleet warships were relatively high (the designs were copied by foreign engineers), and this made the navy the most modem of Poland’s armed forces.