The Stormers won the inaugural United Rugby Championship (URC) title after an 18-13 victory over fellow South African club the Bulls in Cape Town.
A third-minute score from Harold Vorster helped the Bulls into a 7-3 lead at half-time but Evan Roos replied early in the second period.
Andre-Hugo Venter then added a second try for the hosts shortly after Bulls centre Cornal Hendricks was sin-binned.
A late drop-goal from fly-half Manie Libbok sealed the result.
The competition was previously known as the Pro14 but was rebranded for the 2021-22 campaign following the introduction of four sides from South Africa.
The result marked an 11th win in a row for the Stormers, who never won the title during their time in Super Rugby - and were beaten by the Bulls in their only final in 2010.
Stormers come back to lift URC trophy
South African teams had initially struggled for wins in the URC against opponents from Wales, Ireland, Scotland and Italy but finished the season much the stronger after getting used to northern hemisphere conditions and referees.
An attritional clash between the traditional rivals, who contest the country's big north-south derby, was made even more difficult by poor weather and a slippery surface in front of a sell-out 31,000 crowd at the DHL Stadium.
The Pretoria-based Bulls took little over two minutes to strike the first blow, as Johan Grobbelaar capitalised on a brief moment of confusion in the Stormers defence to embark on a penetrating break before offloading to centre Vorster to wriggle over.
Chris Smith added the extras and the visitors continued to look the sharper and more dangerous of the two sides throughout the opening half, but Libbock got the Stormers on the board with a penalty just before the break.
The Bulls briefly restored their seven-point advantage with a Smith penalty at the start of the second half, but the Stormers were soon level.
Number eight Roos stretched over for their first try in the 45th minute after strong forward play, and Libbok converted.
Hendricks then saw yellow for a high tackle and a second Stormers try quickly followed, with replacement hooker Venter finding his way over from a line-out maul just short of the hour.
Smith reduced the lead to two points with a penalty 15 minutes from the end but Libbock's drop goal five minutes from time proved the final score.
Next season the pair will both play in the European Champions Cup, Europe's top continental competition, alongside fellow South African club Sharks, who qualified through their final URC league position.
Stormers: Gelant; Petersen, Nel, Willemse, Senatla; Libbok, Jantjies; Kitshoff (capt), Kotze, Malherbe, Moerat, Orie, Fourie, Dayimani, Roos.
Replacements: Venter, Harris, Fouche, Van Rhyn, Pokomela, Xaba, Masimla, Mngomezulu.
Bulls: Arendse; Moodie, Hendricks, Vorster, Tambwe; C Smith, Burger; G Steenekamp, Grobbelaar, M Smith, W Steenkamp, Nortje, Coetzee (capt), Botha, Louw.
Replacements: Du Plessis, Matanzima, Hunt, Swanepoel, WJ Steenkamp, Papier, Steyn, Kriel.
Sin-bin: Hendricks (56).
Referee: Andrew Brace (Ireland).