No, Aegon V Targaryen (famously known in his youth as "Egg") is not the Mad King. While fans often draw thematic comparisons due to prophecies involving fire, the individual historically known as the "Mad King" in the Game of Thrones universe is actually King Aerys II Targaryen. Egg is chronologically an ancestor—specifically the paternal grandfather—of Aerys II, meaning Egg preceded the Mad King by two generations and died during the catastrophic Tragedy at Summerhall long before Aerys descended into absolute tyranny.