The Harry Potter duo beat out Lord of The Rings' Liv Tyler and Viggo Mortensen and Pirates of the Caribbean lovers Orlando Bloom and Keira Knightley to land atop the new Forbes magazine list.
To formulate the list, Forbes bosses looked at couples who had appeared on screen together more than once in the last 10 years. The money mag then added up the global box office for all of the films they starred in together.
Grint and Watson more than doubled second-placed Tyler and Mortensen's take - with a whopping $6.3 billion.
The top five is:
1. Rupert Grint & Emma Watson (Harry Potter franchise) - $6.3 billion
2. Liv Tyler & Viggo Mortensen (Lord of the Rings franchise) - $3 billion
3. Orlando Bloom & Keira Knightley (Pirates of The Caribbean franchise) - $2.7 billion
4. Leonardo DiCaprio & Kate Winslet (Titanic & Revolutionary Road) - $1.9 billion
5. Robert Pattinson & Kristen Stewart (Twilight franchise) - $1.8 billion