A QTL on 2AL for reducing yellow rust severity was identified from a Chinese wheat landrace, being more effective than Yr18, with evidence for durable resistance from field observations. Utilization of wheat resistance is an important strategy to control yellow rust. The Chinese wheat landrace Hong Qimai (HQM) and the advanced breeding line AQ24788-83 (AQ; a progeny of HQM) can significantly reduce disease severity at the adult-plant growth stage. HQM has maintained adult-plant resistance for a prolonged period of time. To study the inheritance of the resistance, 126 recombinant inbred lines (RILs) derived from the cross Thatcher (TC) × HQM and 138 RILs from Luke × AQ were assessed for disease severity in six field trials. A genetic map of TC × HQM was constructed by genotyping these RILs using the 90 K wheat single-nucleotide polymorphism chip. Luke × AQ map was previously constructed for another disease study and also utilized here. Based on these maps and disease data, a quantitative trait locus (QTL) was detected on the chromosome arm 2AL from both TC × HQM and Luke × AQ and designated as QYr.cau-2AL. The resistance allele at QYr.cau-2AL came from HQM and AQ. QYr.cau-2AL was significantly effective across all the test environments and different genetic backgrounds, with its effect magnitude being higher than that of Yr18. QYr.cau-2AL synergistically acted with Yr18 and a QTL for high-temperature adult-plant resistance on 2BS, resulting in an elevated resistance from the juvenile plant growth stage onward, although QYr.cau-2AL alone displayed no substantial resistance at juvenile stage. Evidence indicates that QYr.cau-2AL is novel and confers durable resistance, and thus, should have high potential value for practical breeding.