Background Acute coronary syndrome (ACS) is a life-threatening disorder which contributes to high morbidity and mortality in the world. Registry of ACS offers a great guidance for improvement and research. We collated a multicentre registry to gain information about demographic, management, and outcomes of ACS in Indonesia. Methods IndONEsia Acute Coronary Syndrome Registry (One ACS Registry) was a prospective nationwide multicenter registry with 14 hospitals participating in submitting data of ACS via standardized electronic case report form (eCRF). Between July 2018 and June 2019, 7634 patients with ACS were registered. This registry recorded baseline characteristics; onset, awareness, and transfer time; physical examination and additional test; diagnosis; in-hospital medications and intervention; complications; and in-hospital outcomes. Results Nearly half of patients (48.8%) were diagnosed with STE-ACS. Most prevalent risk factors were male gender, smoking, hypertension. Patients with NSTE-ACS tended to have more concomitant diseases including diabetes mellitus, dyslipidemia, prior AMI, HF, PCI, and CABG. Majority of ACS patients in our registry (89.4%) were funded by national health coverage. Antiplatelet, anticoagulant, antihypertensive, and statins were prescribed as 24-hours therapy and discharge therapy; however presription of potent P2Y12 inhibitor was low. More STE-ACS patients underwent reperfusion therapy than non-reperfusion (65.2% vs. 34.8%), and primary PCI was the most common method (45.7%). Only 21.8% STE-ACS patients underwent reperfusion strategy within 0-3 hours of onset. Invasive strategy performed in 17.6% of NSTE-ACS patients, and only 6.7% performed early (within