Nadal won at least one Grand Slam singles title in 10 consecutive years, from 2005 through 2014. Counting both endpoints gives ten calendar years: 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 and 2014.
The streak began when Nadal won his first major at the 2005 French Open. Roland-Garros became the centrepiece of the run, but he also won Wimbledon in 2008 and 2010, the Australian Open in 2009, and the US Open in 2010, 2013 and 2014.
This achievement is about winning at least one major in each year, not winning exactly one. Nadal won multiple Grand Slam titles in several seasons, including three in 2010 and two in 2013. He later added major titles in 2017–2020 and 2022, extending his total number of seasons with a Grand Slam victory to 15.