The story of a bold political experiment in nineteenth-century France to establish power through finance. Amid the rise of industrial capitalism and revolutionary turbulence in France, finance was reimagined to be an instrument of economic and social transformation rather than simply a source of private profit, speculation, and inequality. Under Napoleon III's authoritarian regime of the 1850s, the Bonapartist state attempted to use finance to broaden financial securities ownership and sponsor new banking institutions with the promise to direct investment toward infrastructure and industry. But the effort to mobilize financial capital ran into a problem: the financial markets refused to be tamed. Drawing on rich archival sources--from police reports and courtroom transcripts to investment manuals and shareholder petitions-- Capital Untamed reveals how finance grew beyond being an instrument of political power until it escaped control. Robertson captures how the state and its citizens navigated the moment in European capitalism when the social purpose of financial capital had to be determined.