The Titan Army refers to the second army of Greek Titans that began rising during The Sea of Monsters and The Last Olympian. Led by Kronos, The Titan Lord of Time, they fought in every battle in the Second Titan War. Their base of operations was formerly Mount Othrys until it was destroyed by the Roman Demigods from Camp Jupiter.
- Chris Rodriguez (Later joins the Olympian Army)
- Ethan Nakamura (deceased) (Kronos' right-hand man, though he rebeled against him at the last moment, he is killed for it and for his sacrifice he is given a funeral shourd)
- Luke Castellan (deceased) (Controlled by Kronos for most of the The Last Olympian, but he sacrificed himself to destroy Kronos)
- Silena Beauregard (deceased) (acted as a spy for Kronos inside Camp Half-Blood though she wanted to stop but was blackmailed into continuning, however she then atones for it by sacrificing her life to bring the Ares cabin as reinforcements and so she is honoured as a hero.)
- Alabaster Torrington
- Other unnamed soldiers and children of Hecate.
- Kelli, Tammi, and other empousai
- Queen Sess and other Scythian Dracanae
- Pit Scorpion
- Morrain and other Hyperborean Giants
- Cyclopes (the Hyperborean Cyclopes, not Tyson's side of the family who are the Elder Cyclopes and are with the Olympians)
- Laistrygonian Giants
- Colchis Bulls
- Stymphalian Birds
- Dr. Thorn
- Nemean Lion
- Clazmonian Sow
- Lydian drakon
- Aethiopian drakon
- Agrius and Oreius
- Giant Crab
- Sea Serpents, Giant Squid, and other sea monsters.
Following the Battle of Manhattan in The Last Olympian, most of the monsters had been defeated, along with Kronos and Hyperion. The remaining Titans fled and went into hiding. The minor gods were accepted back into Olympus, and presumably given thrones. Prometheus claimed he only wanted to minimize the damage by joining Kronos so he could get out of trouble, but if he was smart he would keep his head down for a couple centuries. In The Lost Hero, it is revealed that Jason Grace, son of Jupiter, led the Roman Demigods to Mount Othrys and destroyed it, while Percy and the demigods of Camp Half-Blood battled Kronos in Manhattan.