The two teams booked their places in the 2024 final following the past weekend's two semi-final matches.
Defending champions WP defeated the Vodacom Bulls 42-28 in the first of Saturday's two semi-finals, which was staged at the City Park in Athlone, Cape Town.
That game was followed by the Lions' encounter with the Hollywoodbets Sharks in Johannesburg, where the hosts claimed a 29-18 victory over the KwaZulu-Natalians.
Because the Highvelders finished top of the log after the league phase, they earned the right to stage this year's final.
WP led the Bulls 20-13 at the halfway stage of their semi-final at City Park, and the Capetonians went on to eventually register a comfortable victory after outscoring their northern rivals by six tries to three.
WP's Junior Bok-laden team had too much firepower for the visitors from Pretoria, with fullback JC Mars leading the way with two tries, while Paul de Villiers (loose forward and last year's SA U20 captain), Joel Leotlela (wing) and Asad Moos (replacement scrumhalf) also joined in the try-scoring act. Imad Khan (scrumhalf) succeeded with three conversions and two penalty goals.
The Bulls' Junior Bok flyhalf Liam Koen also slotted two conversions and three penalty goals, while former SA U20 hooker Juan Smal was one of their three try scorers.
Playing at home in Johannesburg, the Lions made a slow start and found themselves trailing 10-5 at the break, before a strong second-half propelled them to a 29-18 win over the Sharks.
In the end, they registered five tries while the visiting side could only reply with two. Junior Bok utility back Likhona Finca, playing on the left wing, scored a brace of tries for the Highvelders, with flyhalf Sam Francis adding two conversions.
For the Sharks, their No 8 Nick Hatton bagged two tries while replacement flyhalf Frederick Marx contributed a conversion and penalty goal.
Scorers:
DHL Western Province 42 (20), Vodacom Bulls 20 (13)
WP - Tries: JC Mars (2), Paul de Villiers, Damian Markus, Joel Leotlela, Asad Moos. Conversions: Imad Khan (3). Penalty goals: Khan (2).
Bulls - Tries: Juan Smal, Corne Beets, Johan Louw. Conversions: Liam Koen (2). Penalty goals: Koen (3).
Fidelity ADT Lions 29 (5), Sharks 18 (10)
Lions - Tries: Likhona Finca (2), RF Schoeman, Sibabalwe Mahashe, Bronson Mills. Conversions: Sam Francis (2).
Sharks - Tries: Nick Hatton (2). Conversions: Jean Smith, Frederick Marx. Penalty goal: Marx.
The league phase of the SA Rugby U21 Shield competition came to a close this past weekend, with wins for Griquas, Boland and Eastern Province.
Griquas defeated the Pumas 38-18 in Kimberley, Boland edged Border 32-28 in Wellington and EP overpowered SWD 52-15.
The final results mean Boland will host Border this coming Saturday in Wellington, while Griquas are set to welcome the Griffons to Kimberley in the two semi-finals. The final will take place on Saturday, 26 October.