This study aimed to determine Urban Heat Island in Baghdad Governorate capital of Iraq by thermal bands of Landsat 8 images and Geographic Information System. Two cloud free Landsat 8 scenes covering the study area were selected for analysis. These scenes were located at path 168/37 and path 169/37. Images were acquired during daytime at 10:33 AM and it were dated August 19, 2016 and August 26, 2016, respectively. All images mentioned above were registered in Universal Transverse Mercator projection zone 38. Temperatures have been extracted from thermal bands 10 and 11 for each scene and then these results have been merged by mosaic process to produce one scene for band 10 and band 11. Finally, urban heat island has been extracted for study area by taking the average temperatures of band 10 and band 11. The final results shown that Baghdad Governorate contains four heat islands: water body, built-up area, green area, and bare land area. The Heat Island of bare land was highest, followed by green area, built-up area and water body. The highest summer daytime Heat Island was found on bare land (57°C), followed by green area (45 °C),built-up area (43 °C), and water body (37 °C).