The monthly global 2°×2° Extended Reconstructed Sea Surface Temperature (ERSSTv5) has been updated from version 4. This update incorporates a new release of ICOADS R3.0, a decade of near-surface data from Argo floats, and a new estimate of centennial sea ice from HadISST2. Key changes include revised quality control, bias adjustment, and interpolation methods, leading to more realistic spatiotemporal variations and better representation of high-latitude SSTs. Ship SST biases are now calculated relative to more accurate buoy measurements, while the global long-term trend remains unchanged. The reconstructed SST is systematically decreased by 0.077°C due to switching the reference data source from ship SST to modern buoy SST. High-latitude SSTs are decreased by 0.1–0.2°C using sea ice concentration from HadISST2. Cross validations with independent observations show improved representation of spatial variability, El Niño and La Niña events, and decadal SST changes. Long- and short-term SST trends in ERSSTv5 remain significant as in ERSSTv4. The ERSSTv5 includes improvements in reference observations, spatial variability of SSTA, quality screening of in situ data, and new input datasets. These changes enhance the accuracy and reliability of SST reconstructions, particularly in regions with sparse observations. The use of Argo data and updated sea ice concentration improves coverage and timeliness, while adjustments to EOTs and smoothing reduce reconstruction errors. Overall, ERSSTv5 provides a more realistic and accurate representation of historical SST variability and trends.The monthly global 2°×2° Extended Reconstructed Sea Surface Temperature (ERSSTv5) has been updated from version 4. This update incorporates a new release of ICOADS R3.0, a decade of near-surface data from Argo floats, and a new estimate of centennial sea ice from HadISST2. Key changes include revised quality control, bias adjustment, and interpolation methods, leading to more realistic spatiotemporal variations and better representation of high-latitude SSTs. Ship SST biases are now calculated relative to more accurate buoy measurements, while the global long-term trend remains unchanged. The reconstructed SST is systematically decreased by 0.077°C due to switching the reference data source from ship SST to modern buoy SST. High-latitude SSTs are decreased by 0.1–0.2°C using sea ice concentration from HadISST2. Cross validations with independent observations show improved representation of spatial variability, El Niño and La Niña events, and decadal SST changes. Long- and short-term SST trends in ERSSTv5 remain significant as in ERSSTv4. The ERSSTv5 includes improvements in reference observations, spatial variability of SSTA, quality screening of in situ data, and new input datasets. These changes enhance the accuracy and reliability of SST reconstructions, particularly in regions with sparse observations. The use of Argo data and updated sea ice concentration improves coverage and timeliness, while adjustments to EOTs and smoothing reduce reconstruction errors. Overall, ERSSTv5 provides a more realistic and accurate representation of historical SST variability and trends.