According to two American government agencies, NASA and NOAA, 2016 was the hottest year ever recorded (record keeping started in 1880). Both these agencies monitor global surface temperatures, amongst other things. According to NASA, the year 2016 was 0.07°C warmer than the previous record breaking hottest year of 2015. Sixteen of the seventeen warmest years that have ever been recorded have all occurred since 2001. Here is a video showing the temperature of our planet over the years, and here is an image that shows the temperature changes.
Image Credits: http://www.noaa.gov for the earth temperature image
Sources: http://www.noaa.gov, https://www.nasa.gov, https://public.wmo.int