Rising partisan animosity is linked to less support for democracy and more support for political violence. Here we provide a multi-level review of interventions designed to improve partisan animosity, which we define as negative thoughts, feelings, and behaviors towards a political outgroup. We introduce the TRI framework for the three levels of interventions-Thoughts (correcting misconceptions, highlighting commonalities), Relationships (building dialogue skills, fostering positive contact), and Institutions (changing public discourse, transforming political structures)-and connect these levels by highlighting the importance of motivation and mobilization. Our review encompasses both interventions conducted as part of academic research projects, as well as real-world interventions led by practitioners in nonprofit organizations. We also explore the challenges of durability and scalability, examine self-fulfilling polarization and interventions that backfire, and discuss future directions for reducing partisan animosity.