Rapeseed (Brassica napus L. napus), also known as canola in Canada & Australia, oilseed rape in Europe and Asia, is a crucial oilseed crop. It ranks third among the leading oil crops with substantial production in the EU nations, Canada, China, India, and Japan. Its evolutionary lineage traces back to the Miocene period, originating from genus Sinapis (B. nigra) and Diplotaxis-Erucastrum complex (B. oleracea; B. rapa). The early records of rapeseed span from 500 to 12,000 years, influenced by the early agricultural practices and gradual evolution with two ancestral genomes (B. rapa and B. oleracea). The Mediterranean region is the centre of origin for rapeseed, which transitioned from a vegetable to an oil crop throughout the Middle Ages. The discovery of low erucic acid variants in the 1960s significantly enhanced the economic relevance of rapeseed. Its expansion in agriculture is due to the successful breeding efforts focusing on oil and meal quality improvements, notably the development of low-erucic acid and double zero varieties during the 1990s. The challenges faced in varietal development are the complex floral morphology and varied cross-pollination rate (8–80%). The hybrid development was improved after the identification of various sterile lines (CMS; GMS) to overcome the varietal crossing hindrances. Contemporary breeding techniques emphasize the creation of high-yield cultivars with enhanced resilience and stability against abiotic and biotic stresses. Advancements in biotechnology have improved breeding efficiency through the application of TILLING and haploid creation. Many recent studies also used AFLP, SSR, and SNP markers to assess genetic diversity among modern cultivars and landraces and reveal the shifts in the genetic constitution. Such studies on rapeseed breeding emphasize the critical importance of genetic variability and adapting suitable breeding methods via molecular techniques will aid in maintaining genetic diversity and improve future crop traits. The chapter encapsulated key findings and insights regarding the breeding of rapeseed and the significance of genetic diversity in its cultivation, reflecting the historical context and modern advancements.