The painted lady butterfly, Vanessa cardui, has the longest migration routes, the widest hostplant diversity, and one of the most complex wing patterns of any insect. Due to minimal culturing requirements, easily characterized wing pattern elements, and technical feasibility of CRISPR/Cas9 genome editing, V. cardui is emerging as a functional genomics model for diverse research programs. Here, we report a high-quality, annotated genome assembly of the V. cardui genome, generated using 84× coverage of PacBio long-read data, which we assembled into 205 contigs with a total length of 425.4 Mb (N50 = 10.3 Mb). The genome was very complete (single-copy complete Benchmarking Universal Single-Copy Orthologs [BUSCO] 97%), with contigs assembled into presumptive chromosomes using synteny analyses. Our annotation used embryonic, larval, and pupal transcriptomes, and 20 transcriptomes across five different wing developmental stages. Gene annotations showed a high level of accuracy and completeness, with 14,437 predicted protein-coding genes. This annotated genome assembly constitutes an important resource for diverse functional genomic studies ranging from the developmental genetic basis of butterfly color pattern, to coevolution with diverse hostplants.