The paper focuses on the swastika, artefacts of antler, wood, metal and clay marked with the swastika, and swastika-shaped items from the 13th and 14th centuries in the Grand Duchy of Lithuania. An answer is sought to the question what the swastika, a universal sign and symbol, represented in ancient Lithuanian culture and religion, and what kinds of shapes and accompanying mythological meanings it possessed. It is concluded that in the 13th and 14th centuries, the swastika did not have a canon of representation, and its perpendiculars on one-sided items faced in one or the other rotary direction (clockwise or anti-clockwise), while on two-sided ones they faced in both directions simultaneously. Two Lithuanian gods, Perkūnas (Thunder) and Kalvelis (Blacksmith), emerged in the explored contexts of items marked with a swastika. This confirms the genetic connection between the swastika and an equilateral cross, the sign of fire or Thunder, characteristic of the Baltic and ancient Lithuanian religious tradition. To date, there is no reason to believe that the perpendiculars could change the symbolic meaning.