As K-12 STEM education moves toward the integrated application of mathematics and science concepts in collaborative and complex real-world problem solving, there is a commensurate need to redefine what it means to be a STEM teacher in the early grades. Elementary teachers need more than professional development with innovative content and curriculum to be ready to integrate STEM; they need the agency that comes with a strong sense of who they are and who they want to become as STEM teachers. In this commentary, we propose a model for integrated STEM teacher identity with the goal of building a robust definition that is applicable to multiple educational contexts. The model captures the tensions between elementary teachers' multiple identities as STEM learners, professional teachers, and STEM education innovators. Our proposed model structures the complexity of these roles as an intertwining of components from extant professional teacher identity and STEM learner identity models. The careful cultivation of integrated STEM identities has the power to increase teachers' readiness to not only try but to sustain innovative curriculum. Teacher educators and professional development facilitators can use this model to provide more personalized support to teachers. Recommendations for future refinement of this model are offered along with implications for more equitable access to integrated STEM experiences for all students.