Reticulating splines (including many derivative forms) is a phrase included in many Maxis games (or their non-Maxis successors), including SimCity (SimCity 2000 and later), SimCopter, The Sims, The Sims 2, The Sims 3, and The Sims 4. The phrase is most often shown in text while on a load screen, though in its first appearance in SimCity 2000, it was spoken by a female voice. The term has become a somewhat well known in-joke and reference to SimCity or Maxis games in general.

The words 'reticulate' and 'spline' both have dictionary definitions, which has led several people to determine a meaning for the phrase, such as "to make a network of curved elements." However, Will Wright stated in an interview that the term itself is meaningless, as SimCity 2000 does not reticulate splines when generating terrain; the phrase was included in the game because it "sounded cool." It has since been included in many Maxis games, mostly for humor, much like the references to llamas in multiple games.