The paper presents the updates and improvements made to the Extended Reconstructed Sea Surface Temperature (ERSST) dataset from version 4 to version 5. The key upgrades include the use of updated data sources such as ICOADS release 3.0, Argo float data, and HadISST2 sea ice concentration, as well as revisions in quality control, bias adjustment, and interpolation techniques. These changes aim to improve the spatiotemporal realism of reconstructed sea surface temperatures (SSTs), better represent high-latitude SSTs, and correct ship SST biases relative to buoy measurements. Progressive experiments were conducted to evaluate the impact of each change, and cross validations with independent modern observations confirmed the improvements in spatial variability, El Niño and La Niña event magnitudes, and decadal SST changes. The long-term global SST trend remains consistent with previous versions, while short-term trends (2000-2015) show a slight decrease. The paper also discusses the validation datasets, reconstruction methods, and the rationale behind the upgrades, highlighting their significance in enhancing the accuracy and reliability of ERSSTv5.The paper presents the updates and improvements made to the Extended Reconstructed Sea Surface Temperature (ERSST) dataset from version 4 to version 5. The key upgrades include the use of updated data sources such as ICOADS release 3.0, Argo float data, and HadISST2 sea ice concentration, as well as revisions in quality control, bias adjustment, and interpolation techniques. These changes aim to improve the spatiotemporal realism of reconstructed sea surface temperatures (SSTs), better represent high-latitude SSTs, and correct ship SST biases relative to buoy measurements. Progressive experiments were conducted to evaluate the impact of each change, and cross validations with independent modern observations confirmed the improvements in spatial variability, El Niño and La Niña event magnitudes, and decadal SST changes. The long-term global SST trend remains consistent with previous versions, while short-term trends (2000-2015) show a slight decrease. The paper also discusses the validation datasets, reconstruction methods, and the rationale behind the upgrades, highlighting their significance in enhancing the accuracy and reliability of ERSSTv5.