This study addresses the uncertainties in greenhouse gas (GHG) emissions estimates for petrochemical production, which have lacked global quantification, impacting emissions reporting and decarbonization policymaking. The analysis covers 81 chemicals at 37,000 facilities worldwide, assessing six uncertainty sources. The results show a 34% uncertainty in total global emissions of 1.9 ± 0.6 Gt CO₂-eq for 2020, with uncertainties ranging from 15% to 40% across most petrochemicals. The largest uncertainties stem from the inability to assign specific production processes to facilities due to data limitations. Uncertain data on feedstock production and off-site energy generation also contribute significantly, while on-site fuel combustion and chemical reactions have smaller roles. Allocation method choices for co-products are generally insignificant. Prioritizing facility-level process specification in data collection for just 20% of facilities could reduce global uncertainty by 80%. This highlights the necessity of quantifying uncertainty in petrochemical GHG emissions globally and outlines priorities for improved reporting. The dataset generated offers independent emissions factor estimates based on facility-specific information for 81 chemicals, supporting future analyses.This study addresses the uncertainties in greenhouse gas (GHG) emissions estimates for petrochemical production, which have lacked global quantification, impacting emissions reporting and decarbonization policymaking. The analysis covers 81 chemicals at 37,000 facilities worldwide, assessing six uncertainty sources. The results show a 34% uncertainty in total global emissions of 1.9 ± 0.6 Gt CO₂-eq for 2020, with uncertainties ranging from 15% to 40% across most petrochemicals. The largest uncertainties stem from the inability to assign specific production processes to facilities due to data limitations. Uncertain data on feedstock production and off-site energy generation also contribute significantly, while on-site fuel combustion and chemical reactions have smaller roles. Allocation method choices for co-products are generally insignificant. Prioritizing facility-level process specification in data collection for just 20% of facilities could reduce global uncertainty by 80%. This highlights the necessity of quantifying uncertainty in petrochemical GHG emissions globally and outlines priorities for improved reporting. The dataset generated offers independent emissions factor estimates based on facility-specific information for 81 chemicals, supporting future analyses.