Club record signing Mounie, back in the starting line-up after recently returning to full fitness, grabbed his first goal since the opening day of the season in the 12th minute of the encounter.
The Benin forward then headed his second just before half-time to help the Terriers halt a four-game losing run and condemn the Seagulls to five games without a league win.
Have a look below at the quick-fire highlights from the John Smith's Stadium.
5 Minutes: Jonas Lossl saves well from a Glenn Murray header but the Brighton forward is ruled offside anyway.
7 Minutes: Poor defending from Dale Stephens lets Steve Mounie in who’s left-footed volley is well saved by Mat Ryan in the Brighton goal.
12 Minutes: GOAL! A Chris Lowe corner is flicked on by Christopher Schindler at the near post and Mounie is on hand to bundle the ball home.
33 Minutes: Lowe whips in a teasing ball which just misses Mounie and the Brighton keeper and goes out of play.
35 Minutes: Markus Suttner curls a free-kick into the box but Jonathan Hogg clears with a diving header.
43 Minutes: GOAL! The visitors fail to clear Lowe's corner and Mathias 'Zanka' Jorgensen’s header finds Mounie who's header makes it 2-0.
47 Minutes: A superb block from Lowe thwarts Pascal Gross’ shot.
57 Minutes: Collin Quaner drives at the Brighton defence and cuts the ball back to Mounie who blazes over the bar.
59 Minutes: Brighton’s keeper denies Elias Kachunga’s fierce effort from a tight angle at the near post.
62 Minutes: A Mounie cross strikes Lewis Dunk in the area but nothing is given.
69 Minutes: Smith is inches away with a curling effort which goes just wide of the post.
70 Minutes: Brighton defender Shane Duffy is forced to slice a clearance over his own bar.
77 Minutes: Mounie creates room for himself before drilling just over the bar.
83 Minutes: Ince is put through by Quaner - he goes past Suttner but Brighton’s keeper saves well.
Huddersfield Town (4-2-3-1): Lossl; Schindler, Zanka, Lowe, Smith; Hogg, Mooy; Quaner, Ince (Lolley, 86’), Kachunga (Williams, 89’); Mounie (Depoitre, 85’)
Subs Not Used: Coleman, Whitehead, Cranie, Hadergjonaj
Brighton & Hove Albion (4-5-1): Ryan; Bruno, Duffy, Dunk, Suttner; Schelotto (March, 46’), Stephens, Propper, Brown (Hemed, 73’), Gross (Izquierdo, 63’); Murray
Subs Not Used: Krul, Huenemeier, Kayal, Izquierdo, Baldock
Half Time: Huddersfield Town 2 Brighton & Hove Albion 0
Next Match: Chelsea FC at the John Smith’s Stadium, Premier League, Tuesday, December 12 (kick-off 8pm)