This study reports a genome-wide association meta-analysis of 18,381 autism spectrum disorder (ASD) cases and 27,969 controls, identifying five genome-wide significant loci. By leveraging genetic correlation with other complex traits (schizophrenia, major depression, and educational attainment), seven additional loci shared with these traits are identified. The polygenic architecture of ASD is characterized by both quantitative and qualitative heterogeneity across subtypes, with higher heritability in Asperger's syndrome and lower in cases with intellectual disability. Functional analyses using Hi-C data from fetal brains and brain transcriptome data highlight the involvement of processes related to brain development and neuronal function. These findings establish a robust set of common variant associations in ASD and lay the groundwork for better understanding the biology of ASD and related phenotypes.This study reports a genome-wide association meta-analysis of 18,381 autism spectrum disorder (ASD) cases and 27,969 controls, identifying five genome-wide significant loci. By leveraging genetic correlation with other complex traits (schizophrenia, major depression, and educational attainment), seven additional loci shared with these traits are identified. The polygenic architecture of ASD is characterized by both quantitative and qualitative heterogeneity across subtypes, with higher heritability in Asperger's syndrome and lower in cases with intellectual disability. Functional analyses using Hi-C data from fetal brains and brain transcriptome data highlight the involvement of processes related to brain development and neuronal function. These findings establish a robust set of common variant associations in ASD and lay the groundwork for better understanding the biology of ASD and related phenotypes.