The fourth and final season of the reimagined science fiction television series Battlestar Galactica premiered on the Sci-Fi Channel in the United States on April 4, 2008, and concluded on March 20, 2009. Similar to the second season, it was split into two parts, each containing 10 episodes. "Season 4.0" aired from April to June 2008 and "Season 4.5" aired from January to March 2009. The fourth season contained 20 episodes, plus the television film Razor.

The third season of the reimagined science fiction television series Battlestar Galactica premiered on Sci Fi in the United States on October 6, 2006, and concluded on March 25, 2007. Unlike the previous season, it was not split into two parts and did not have an extended hiatus during the middle of the season. The third season contained 20 episodes.