Objectives: To investigate alterations in depicted penis size by evaluating nude male paintings from the 15th to 21st centuries. Materials and Methods: Nude-male paintings were identified from various art history websites and analysed to determine changes in penis size over time. Two observers organised the paintings according to the century in which they were created and made the calculations. Penile length to ear length (PtEL) or penile length to nose length (PtNL) were calculated to standardise the measurements using professional image analysis software. PtEL was first attempted for all paintings; if PtEL could not be ascertained, then nose length was used instead of the ear, as the nose length is defined as equal to ear length according to the golden ratio. Thus, PtNL was ensured and both ratios were then referred to using a common term: penis depiction ratio (PDR). Further analysis was performed by dividing the paintings into three groups according to the historical development of art: Renaissance Period (1400–1599; 15th–16th centuries), Baroque–Rococo and Impressionism Period (1600–1899; 17th–19th centuries) and Contemporary Art Period (1900–2020; 20th and 21st centuries). Results: Of 232 identified paintings, 72 (31.1%) were excluded because they depicted images of adolescents or an erect penis. The PDR was found to differ significantly between paintings created in different centuries (P < 0.001). Subgroup analysis revealed that paintings from the 21st century demonstrated significantly higher PDRs than paintings from previous centuries (P = 0.001). Conclusions: In paintings depicting nude males, the size of the penis has gradually increased throughout the past seven centuries, and especially after the 20th century. This observation illustrates the changing sociocultural inputs into male body image and emphasises the need for improved understanding of the sociocultural factors associated with the perception of penis size in men.