The sensitivity of electrocardiogram (ECG) criteria to detect left ventricular hypertrophy (LVH) is low, especially in women. We determined sex-specific sensitivities of ECG-LVH criteria, and developed new criteria, using cardiovascular magnetic resonance imaging (CMR). Sensitivities of ECG-LVH criteria were determined in participants of the UK Biobank (N = 3632). LVH was defined when left ventricular mass was > 95% confidence interval (CI) according to age and sex. In a training cohort (75%, N = 2724), sex-specific ECG-LVH criteria were developed by investigating all possible sums of QRS-amplitudes in all 12 leads, and selecting the sum with the highest pseudo-R2 and area under the curve to detect LVH. Performance was assessed in a validation cohort (25%, N = 908), and association with blood pressure change was investigated in an independent cohort. Sensitivities of ECG-LVH criteria were low, especially in women. Newly developed Groningen-LVH criterion for women (QV2 + RI + RV5 + RV6 + SV2 + SV4 + SV5 + SV6) outperformed all ECG-LVH criteria with a sensitivity of 42% (95% CI 35-49%). In men, newly developed criterion ((RI + RV5 + SII + SV2 + SV6) × QRS duration) was equally sensitive as 12-lead sum with a sensitivity of 44% (95% CI 37-51%) and outperformed the other criteria. In an independent cohort, the Groningen-LVH criteria were strongest associated with change in systolic blood pressure. Our proposed CMR sex-specific Groningen-LVH criteria improve the sensitivity to detect LVH, especially in women. Further validation and its association with clinical outcomes is warranted.