e23291 Background: Hematologic cancers (HCs) in Southeast Asia (SEA), a diverse population of over 680 million, are still understudied. Data from the 2020 Global Cancer Observatory (GCO) was used to estimate the incidence and mortality of HCs in the region to provide direction for effective disease control and improve population outcomes. Methods: The International Agency for Research on Cancer’s publicly available GCO data aggregates global cancer incidence and mortality. We report cumulative incidence rate (CIR) and cumulative mortality rate (CMR) defined per 100,000 people, and weighted average age-standardized incidence rate (ASIR) and age-standardized mortality rate (ASMR) in 2020. Data for Hodgkin Lymphoma (HL), Non-Hodgkin's Lymphoma (NHL), Leukemia, and Multiple Myeloma (MM) in the world, in SEA, and in the 11 individual SEA countries are presented. Results: The table presents CIR, ASIR, CMR, and ASMR of hematologic cancers in SEA compared to overall global data. CIR, ASIR, CMR, and ASMR were higher for males than females in SEA. For NHL, CIR was highest in Singapore (18.8), Thailand (10.2), and Brunei (9.6) and lowest in Myanmar & Cambodia (3.6), and Timor-Leste (2.7). ASIR trends were parallel albeit differences were smaller. CMR was highest in Singapore (6.2) and Thailand (5.9) and lowest in Timor-Leste (1.5). ASMR was highest in Brunei (4.5) and lowest in Timor-Leste (2.0). For leukemia, CIR was highest in Singapore (11.1) and lowest in Myanmar (3.1) and Timor-Leste (2.6); ASIR was highest in Singapore (8.9) and lowest in Myanmar (3.2) and Timor-Leste (2.9). CMR was highest in Singapore (5.2) and lowest in Myanmar (2.6) and Timor-Leste (2.3). ASMR was highest in Lao PDR (4.7) and Vietnam (4.5), and lowest in Singapore (3.1) and Timor-Leste (2.9). For MM, CIR was highest in Singapore (4.1), ASIR was highest in Brunei (2.4) and both are lowest in Myanmar (0.4). CMR was highest in Singapore & Thailand (1.8) and lowest in Myanmar (0.35); ASMR rates were similar. For HL, CIR was highest in Brunei Darussalam (1.8) and Singapore (1.4) and lowest in Myanmar (0.2). ASIR trends were similar. CMR was highest in Vietnam (0.26) and lowest in Singapore (0.1) and Myanmar (0.08). ASMR trends were similar. Conclusions: Despite lower regional average incidence and mortality, significant intra-regional variations exist reflecting disparities in the management of HCs. In addition, while data suggests lower disease burden in SEA, mortality rates are still comparable and in some cases worse than the global average. More work is needed to investigate HC epidemiology in SEA to inform cancer control in the region and improve its blood cancer outcomes. [Table: see text]