Electronic Journal of Differential Equations, Vol. 2021 (2021), No. 47, pp. 1-20. Title: Existence and asymptotic behavior of positive least energy solutions for coupled nonlinear Choquard equations Authors: Song You (Tsinghua Univ., Beijing, China) Peihao Zhao (Lanzhou Univ., Gansu, China) Qingxuan Wang (Zhejiang Normal Univ., Jinhua, Zhejiang, China) Abstract: In this article, we study the coupled nonlinear Schrödinger equations with Choquard type nonlinearities $$\displylines{ -\Delta u+\nu_1u=\mu_1(\frac{1}{|x|^{\alpha}} *u^2)u +\beta (\frac{1}{|x|^{\alpha}} *v^2)u \quad\text{in } \mathbb{R}^{N},\cr -\Delta v+\nu_2v=\mu_2(\frac{1}{|x|^{\alpha}} *v^2)v +\beta (\frac{1}{|x|^{\alpha}} *u^2)v \quad\text{in } \mathbb{R}^{N},\cr u,v \geq 0\quad \text{in } \mathbb{R}^{N}, \quad u,v \in H^{1}(\mathbb{R}^{N}), }$$ where ν1212 are positive constants, β>0 is a coupling constant, N≥3, α in (0,N) ∩ (0,4), and "*" is the convolution operator. We show that the nonlocal elliptic system has a positive least energy solution for positive small β and positive large β via variational methods. For the case in which ν12, μ1≄μ2, N=3,4,5 and α=N-2, we prove the uniqueness of positive least energy solutions. Moreover, the asymptotic behaviors of the positive least energy solutions as β→ 0+ are studied. Submitted July 17, 2019. Published May 28, 2021. Math Subject Classifications: 35B40, 35J47, 35J50. Key Words: Coupled Choquard equations; positive least energy solution; asymptotic behavior; variational method.