It was the third time in four outings this season that Llanelli had turned over their main rivals for the title of top "official" side in Wales. Just how good this current Llanelli side is will now be put to the test in the semi-finals, when they face old rivals Cardiff on 17 April.
If they can beat one set of rebels in that match then they are likely to meet another, in the shape of Swansea, in the final at Ninian Park on 16 May.
Swansea, who put Ebbw Vale to the sword 42-14, have to face Division One's Cross Keys in the other semi-final.
The man who turned the tide was the prop John Davies, whose try five minutes into the second half put Llanelli ahead for the first time. Until then it had been a battle of two of the biggest and most prolific boots in the Welsh game, Neil Jenkins landing four penalties to Byron Hayward's two.
Hayward's conversion of Davies' try, which came from a clever inside pass from Wayne Proctor, meant Ponty were forced to chase. Hayward's third penalty made life even more difficult for the home side, and led to a certain amount of panic creeping in.
But Ponty never give anything other than 100 per cent effort and commitment in front of their home crowd and when the right wing Gareth Wyatt rounded the Tongan giant Salesi Finau in the 56th minute to put his side back in front the match was again in the melting pot.
This season, though, Llanelli have emerged as a team with a bigger heart, and that slender deficit was soon overtaken by Hayward's fourth penalty.
Then two unlikely events showed just how desperate both teams were to win. It was obvious that home skipper, Jenkins, was becoming increasingly frustrated with the way things were going and indulged in too much conversation with the referee David Davies on the hour. The result was 10 minutes in the sin-bin.
While Jenkins was cooling down, Hayward kicked his fifth and final penalty to ram another nail into the Ponty coffin. As hard as the home team tried, they were unable to break a Llanelli defensive line led manfully by flankers Ian Boobyer and Hywel Jenkins, and another cup tie went west.
There was one final chance of glory in the closing minutes, when the Llanelli scrum half Rupert Moon followed Jenkins into the cooler for deliberately killing the ball. But the thin red line held firm and the cup holders booked their ticket into the next round.
Pontypridd: Try Wyatt; Penalties Jenkins 4. Llanelli: Try Davies; Conversion Hayward; Penalties Hayward 5.
Pontypridd: K Morgan; G Wyatt, D James, S Lewis, R Shorney (G O Lewis, 21); N Jankins (capt), P John; M Griffiths, A Lamerton (T Billups, 66), N Tau, G Prosser, I Gough, G P Lewis (N Thomas, 70), D McIntosh (M LLoyd, 65), M Williams.
Llanelli: B Hayward; W Proctor, N Davies, N Boobyer, S Finau; S Jones, R Moon; M Madden, R McBryde (capt), J Davies, C Wyatt, M Voyle, H Jenkins (A Thomas, 79), S Quinnell, I Boobyer.
Referee: D R Davies (Llanbradach).Reuse content