Phytophthora root and stem rot (PRSR) caused by Phytophthora sojae is the most destructive soybean soil-borne disease worldwide. Discovery of genes conferring broad-spectrum resistance to the pathogen is an urgent need to prevent the outbreak of the disease. Here we show that soybean Rps11 is a 27.7-kb nucleotide-binding site-leucine-rich repeat (NBS-LRR or NLR) gene conferring extreme broad-spectrum resistance to the pathogen. Rps11 is located in a genomic region harboring a cluster of unusually large NLR genes belonging to a single evolutionary lineage that is distinct from all other lineages in the soybean genome, and was derived from rounds of intergenic and intragenic unequal recombination. Such recombination events have resulted in promoter fusion and expansion of the LRR domain that presumably explains such broadness of the resistance spectrum. The NLR gene cluster exhibits drastic structural diversification among phylogenetically representative varieties, including gene copy number variation ranging from five to 23 copies, and absence of allelic copies of Rps11 (i.e., rps11) in any of the non-Rps11-donor varieties examined. Our study thus exemplifies innovative evolution of NLR genes and NLR gene clusters and will accelerate the deployment of Rps11 for soybean protection.