The author of the Stadiasmus Maris Magni (or Periplus Maris Magni) is anonymous, a figure known only through a single surviving practical guide for sailors. The date of the work is highly uncertain, with scholarly estimates ranging from the 1st to the 6th century CE. Some scholars believe the text may be a compilation that incorporates material from different periods. The anonymous geographer was likely a Greek-speaking sailor or editor, writing a functional manual for maritime navigation based on earlier sources.

The work is a periplous, a coastal sailing guide for the entire Mediterranean Sea. It systematically lists harbors, landmarks, and the distances between them measured in stadia. This text survives in just one known manuscript from the medieval period.

According to modern scholars, the Stadiasmus Maris Magni is a significant historical source precisely because of its practical, non-theoretical nature. It provides a detailed snapshot of late antique trade routes, coastal geography, and sailing practices, preserving many place names and measurements. Its value is enhanced because it was copied alongside other important geographical works in the same manuscript collection.