strv fm/31, "tank trial model-1931") was a Swedish late interwar era medium tank constructed by AB Landsverk for the Swedish Army between 1930[4] and 1935,[2] featuring welded armour joints and a "wheel-cum-track system", allowing for interchangeable wheeled and tracked propulsion.

[4][5] Beyond the wheel-track suspension, it was almost identical to the Landsverk L-10 design, featuring an advanced all-welded construction, using periscopes for visibility rather than view slits.

The lone L-30 (designated stridsvagn fm/31: fm = försöksmodell, "trial model") was intended simply for mobility trials and was produced using mild steel from Landsverk, lacking the frontal hull machine gun port of the L-10 and featuring a wooden mockup turret.

Production was delayed and the prototype was produced and delivered to the Swedish Army in 1935.

[4][2] Despite being highly advanced for its time, the design was seen as too expensive and specialized, thus in the end it was cancelled in favour of conventional tanks.