The 2021 Football South Australia Federation Cup, also known as the 2021 FFA Cup South Australian preliminary rounds until the semi-finals,^[1] was the 108th running of the Federation Cup, the main soccer knockout cup competition in South Australia. The competition also functioned as part of the 2021 FFA Cup preliminary rounds, with the two finalists qualifying for the main knockout competition.

Adelaide Olympic were champions for the second time, defeating Adelaide City 2–1 in the final,^[2] defending their 2019 title.^[3]

Adelaide (49)

Gawler (1)

Ade. Hills (2)

Port Pirie (1)

Location of teams participating in the Federation Cup

A total of 52 teams participated in the competition, 49 from the Greater Adelaide area, two from the Adelaide Hills region and one from Gawler and Port Pirie. National Premier Leagues South Australia, State League One and State League Two represent levels 2–4 on the unofficial Australian league system and are required to participate in the Federation Cup. The South Australian Regional Leagues represent level 5. The South Australian Amateur Soccer League is not represented on the national league system. Adelaide United Youth are not eligibile for the tournament, as the senior team entered the FFA Cup competition at the Round of 32.

The first round of the Federation Cup was also the third round of the 2021 FFA Cup preliminary rounds. Fulham United (3) received a bye to the second round.

Times before 4 April are in ACDT, times on or after 4 April are in ACST

USC Lion (-) v Pontian Eagles (4)

24 March	USC Lion (-)	0–2	Pontian Eagles (4)	Grange
19:30		Report	Koutoulogenis 3', 20'	Stadium: Grange Reserve

Western Strikers (3) v Elizabeth Downs (-)

26 March	Western Strikers (3)	1–3	Elizabeth Downs (-)	Royal Park
19:30	Katsigiannis 51'	Report	Brennan 17' Gundlach 51', 54'	Stadium: Carnegie Reserve

Gawler Eagles (4) v West Torrens Birkalla (3)

26 March	Gawler Eagles (4)	1–2	West Torrens Birkalla (3)	Evanston Gardens
19:30	Cook 71'	Report	Makridis 13' Mbarga 31'	Stadium: Karbeethan Reserve

Adelaide Red Blue Eagles (-) v Salisbury United (4)

26 March	Adelaide Red Blue Eagles (-)	2–4	Salisbury United (4)	Burton
19:30	Hennan 31', 68'	Report	Martyn 39' (pen.), 57' (pen.) Greaves 71' Bigirimana 90+2'	Stadium: Steve Jarvis Park

Modbury Jets (3) v Eastern United (3)

27 March	Modbury Jets (3)	2–1	Eastern United (3)	Ridgehaven
15:00	Radice 2' Doyle 81'	Report	Dello 65'	Stadium: Smith Partners Stadium

Northern Demons (4) v Adelaide Thunder (-)

27 March	Northern Demons (4)	1–0	Adelaide Thunder (-)	Port Pirie
15:30	Capurso 4' (pen.)	Report		Stadium: Byrne Park

Port Adelaide Pirates (4) v Vipers FC (4)

27 March	Port Adelaide Pirates (4)	4–1	Vipers FC (4)	Taperoo
19:00	Skeffington 44' Williams 47' Marchioro 61' Anderson 84'	Report	Ibrahim 45'	Stadium: Ngarrpadla Josie Agius Reserve

Ghan Kilburn City (-) v Adelaide Titans (-)

14 April	Ghan Kilburn City (-)	6–1	Adelaide Titans (-)	Angle Park
19:30	Pearce 14' (o.g.) Kamara 21', 47' Abbasi 38' Dadzie 59' Hussaini 82' (pen.)	Report	Mangafakis 22'	Stadium: VALO Football Centre

The second round of the Federation Cup was also the fourth round of the 2021 FFA Cup preliminary rounds, featuring 21 teams from the previous round and the 11 teams from the National Premier Leagues South Australia.

All times are in ACST

BOSA FC (-) v Modbury Jets (3)

23 April	BOSA FC (-)	1–5	Modbury Jets (3)	Prospect
19:30	Muhoma 50' (o.g.)	Report	Pollock 12' (pen.) Mitchell 22' (o.g.) Wegener 59' Barr 66', 77'	Stadium: Charles Cane Reserve

Adelaide City (2) v Adelaide Hills Hawks (3)

24 April	Adelaide City (2)	3–2	Adelaide Hills Hawks (3)	Oakden
14:30	Irabona 44', 57' Halliday 90+1'	Report	Tredrea 18', 35'	Stadium: Adelaide City Park

Adelaide Comets (2) v Mount Barker United (4)

24 April	Adelaide Comets (2)	9–1	Mount Barker United (4)	Adelaide
14:30	Beric 18', 21', 60' Andijanto 34' Lobasso 47' Mavrolambados 52' Keramidas 65' Diamantis 70' Dimou 88'	Report	Pienaar 25'	Stadium: Park 24

Playford City Patriots (3) v Adelaide Blue Eagles (2)

24 April	Playford City Patriots (3)	2–1	Adelaide Blue Eagles (2)	Edinburgh North
15:00	Kurtz 6' Ryan 45'	Report	Matsumoto 8'	Stadium: Ramsay Park

The Cove (4) v Fulham United (3)

24 April	The Cove (4)	1–2 (a.e.t.)	Fulham United (3)	Hallett Cove
18:00	Moon 9'	Report	Mittiga 56' Takos 118'	Stadium: Cove Sports and Community Centre

Adelaide Olympic (2) v Adelaide University (4)

24 April	Adelaide Olympic (2)	1–0	Adelaide University (4)	Angle Park
18:00	Konstandopoulos 62'	Report		Stadium: VALO Football Centre

The third round of the Federation Cup was also the fifth round of the 2021 FFA Cup preliminary rounds.

All times are in ACST

Modbury Jets (3) v Sturt Lions (2)

15 May	Modbury Jets (3)	0–1	Sturt Lions (2)	Ridgehaven
14:30		Report	Rodriguez 72' (pen.)	Stadium: Smith Partners Stadium

Salisbury United (4) v Croydon Kings (2)

15 May	Salisbury United (4)	1–1 (a.e.t.) (4–5 p)	Croydon Kings (2)	Burton
14:30	McDevitt 47'	Report	Stefanopoulos 32'	Stadium: Steve Jarvis Park

Fulham United (3) v Adelaide Olympic (2)

15 May	Fulham United (3)	1–3	Adelaide Olympic (2)	West Beach
14:30	Tsialafos 90+3'	Report	Bontor 27' Jones 40' Pounendis 75'	Stadium: West Beach Parks Football Centre

The quarter-finals of the Federation Cup was also the sixth round of the 2021 FFA Cup preliminary rounds.

All times are in ACST

Campbelltown City (2) v Adelaide Comets (2)

8 June	Campbelltown City (2)	4–1	Adelaide Comets (2)	Newton
19:30	Mullen 7' Marino 12', 73' Ditroia 16'	Report	Diamantis 22'	Stadium: Steve Woodcock Sports Centre

Adelaide Olympic (2) v Croydon Kings (2)

9 June	Adelaide Olympic (2)	2–0	Croydon Kings (2)	Angle Park
19:30	Simosis 68', 75'	Report		Stadium: VALO Football Centre

The semi-finals of the Federation Cup was also the seventh round of the 2021 FFA Cup preliminary rounds, with the two winners qualifying for the 2021 FFA Cup.

All times are in ACST

Adelaide Olympic (2) v Campbelltown City (2)

22 June	Adelaide Olympic (2)	1–0	Campbelltown City (2)	Angle Park
19:30	Cittadini 54'	Report		Stadium: VALO Football Centre

• 2021 Football South Australia season