Background: Elevated blood pressure (BP) is a major contributor to coronary artery disease. We explored the impact of life-course BP on later-life normalized stress myocardial blood flow (sMBFN) and perfusion reserve (MPR) by cardiovascular magnetic resonance (CMR). Methods: MyoFit46 (NCT05455125) prospectively recruited ~500 National Survey of Health and Development 1946 birth cohort participants aged ~77 years to undergo stress perfusion and late gadolinium enhancement (LGE) CMR. Systolic (SBPs) and diastolic BPs (DBPs) were recorded at 36, 43, 53, 63, 69, and 77 years. For each participant, annual rates of BP change (steepness) and area under BP trajectory curve (AUCBP; cumulative burden) were derived using mixed-effects models. BP-CMR perfusion associations were tested using generalized models, adjusted for antihypertensive use, demographics, lifestyle, and comorbidities. Cross-sectional associations between with major adverse cardiovascular events (MACE: myocardial infarction, stroke, and heart failure) were also tested. Mediation analyses explored mechanistic pathways. Results: Among 459 participants, each 10mmHg higher SBP at 36 to 69 years associated with 3-6% lower sMBFN at 77 years. At 43-63 years, as SBPs rose from 120 to 140mmHg, sMBFN was 18-24% lower. Having a sustained higher SBP by 10mmHg from 36 to 77 years associated with 11% (95% CI: 8-14) lower sMBFN. Each 1 mmHg/year steeper SBP rise during age intervals 36–43, 43–53, 53–63, and 63–69 associated with 2–5% lower sMBFN at 77 years, association not conditional on baseline or final BPs in each interval. Associations may be clinically relevant as each 1% lower sMBFN associated with 3% higher MACE odds. sMBFN mediated 20-40% of the life-course SBPs-LGE associations. Results were similar for DBP, MPR, or sMBF. Conclusions: Higher life-course BPs, steeper increases, and greater cumulative burden associate with lower myocardial perfusion at 77 years, which can be linked with higher MACE odds and fibrosis burden. This underscores the importance of early-life screening and guiding treatment based on BP trajectories.