Title: UNICO: Efficient Unified Hardware-Software Co-Optimization For Deep Neural Networks. Abstract: Specialized hardware has become an indispensable component to deep neural network acceleration. To keep up with the rapid evolution of neural networks, recently, holistic and automated solutions for jointly optimizing both hardware architectures and software mapping have been proposed. In this paper, we propose UNICO, a Unified Co-Optimization framework for hardware-software co-design, aimed at addressing the efficiency issues of vast design space exploration and the issue of overfitting to specific input neural network workloads that are facing current approaches. UNICO employs multi-objective Bayesian optimization to sample hardware, and  performs parallel and adaptive software mapping search for hardware samples with a customized successive halving algorithm. To reduce overfitting, UNICO incorporates quantitative robustness measures to guide the proposed search and evaluation procedure. Experiments performed for both open-source spatial accelerators and a real-word commercial environment show that UNICO significantly improves over its counterparts, finding not only superior but also more robust hardware configurations, yet at drastically lower search cost.