is there an rpg with No Final boss?

[Madame Adequate]

ME3 doesn't really have a final boss, unless you count talking/shooting the Illusive Man but that's way scripted than a real boss setting.

Someone forgot the heroic Marauder Shields

[Fynn]

While there is a final boss in the games, Shin Megami Tensei 1 had this amusing thing where your final boss is determined by your alignment. What makes it amusing is that depending on your alignment, you could actually recruit the final boss of your own alignment and use them to beat up the opposing alignment boss.

Also DQVI has an optional boss you can fight who is way more powerful than the final boss. Beating him though has him destroy the final boss for you.

But you can't do this the first time you beat the game. To access the optional dungeon to that optional boss you first need to beat the main story and load up your save file.

[FFNut]

Would the Harvest Moon series qualify as he have a goal, but there really isn't a battle system to fight and it is qualified as a RPG still in terms of play style.

[Sephiroth]

Atelier Rorona never had any kind of final boss battle.

Eh ~

If you want to get all the stuff for all endings and ultimately True Ending and all trophies you have to beat Masked G, Iron Giant, all Dragons and the Demon. The last one is normally the Demon. He might not be a "traditional" final boss but he is here.

Depending on how much you want to call a Hack 'n Slay like Drakengard an RPG and then want to "disqualify" the last battle as a "Final Boss" Battle for the entire reason that it consits of an idiotic rhythmic game you might say the Mother Angel on Timeline E and Deflowering Zero on Timeline D for Drakengard 1 and Drakengard 3 are no final bosses.

I call them final bosses nonetheless.