The 1978 Nations Cup, also known by its sponsored name Ambre Solaire Nations Cup, was a men's team tennis tournament played on outdoor clay courts.

It was the second edition of the Nations Cup and the event was part of the 1978 Grand Prix circuit.

Spain defeated Australia in the final, watched by a crowd of nearly 7,000, to win the title for the first time and earn the $60,000 first-prize money.

[2][3] The draw consisted of eight teams divided over two round-robin groups.

The two best ranked teams from each group proceeded to the semifinals.