Springbok wing Cheslin Kolbe, who has surely booked his World Cup place with a series of brilliant performances for Toulouse this year, was well watched in the Top 14 final on Saturday but assisted in two tries to help his side to the title.
Toulouse, with their close 24-18 win over Clermont, secured their 20th title and finished the season top of the standings.
Toulouse scored two tries, and Kolbe had a hand in both. For the first, Kolbe took a wide arching run targeting a vulnerable Alivereti Raka and fed Yoann Huget who went over in the corner.
Kolbe was then shown a yellow card for an early tackle after 33 minutes.
Huget scored either side of the break as Toulouse lifted the title in their first final appearance since 2012.
Clermont, who scored a record number of tries, failed in their attempt to win a European and league double after lifting the Challenge Cup in May despite a flawless kicking performance from Scotland's Greig Laidlaw who kicked five from five penalty attempts with another coming from Camille Lopez.
Toulouse: Tries: Yoann Huget (2). Conversion: Thomas Ramos. Penalties: Ramos (4).
Clermont: Penalties: Greig Laidlaw (5), Camille Lopez.