Ronnja is a female name.
Ronnja is a variant of the Russian name Ronja, which is a short form of the names Roxana or Veronika. Besides, Ronja is an invented name by the Swedish author Astrid Lindgren for her book “Ronia the Robber’s Daughter” (“Ronja rövardotter”). She had derived the name from the north Swedish lake JuRONJAure. Ronnja is also a feminine form of the Old Norse name Ragnvaldr and a diminutive of the Greek name Siphronia.
Ronnja means “bright” and “dawn” (from Roxana) and “true image” or “winner” (from Veronika). Besides, Ronja means “the advice of the ruler” (from Old Norse “regin” = advice/counsel (of the gods) + “valdr” = ruler/power) and “self-controlled”, “sensible” (from Sophronia).