Alonso claimed his second victory in three races this season when he established an early lead then held off McLaren's [ Images ] Kimi Raikkonen [ Images ] on a dramatic afternoon at Melbourne's [ Images ] Albert Park.
Officials introduced the safety car on four separate occassions to clear the track of debris as almost half the field failed to complete the race.
Alonso's Italian team mate Giancarlo Fisichella [ Images ], winner of last year's Australian GP and last month's Malaysian GP, finished fifth while Canada's [ Images ] Jacques Villeneuve was sixth for BMW Sauber.
Britain's Jenson Button [ Images ], who started on pole position, would have finished fourth but his Honda engine blew up less than 100 metres from the finish line and he pulled over.
Alonso has 28 points to Raikkonen and Fisichella's 14.
Renault [ Images ], winner of all three races so far this season, lead the constructors' standings with 42 points to McLaren's 23.
1. Fernando Alonso (Spain) Renault 1:34:27.870
2. Kimi Raikkonen (Finland) McLaren +00:01.829
3. Ralf Schumacher (Germany [ Images ]) Toyota 00:24.824
4. Nick Heidfeld (Germany) BMW Sauber 00:31.032
5. Giancarlo Fisichella (Italy [ Images ]) Renault 00:38.421
6. Jacques Villeneuve (Canada) BMW Sauber 00:49.554
8. Scott Speed (U.S.) Toro Rosso - Cosworth 00:53.817
9. David Coulthard [ Images ] (Britain) RedBull - Ferrari 00:53.983
10r. Jenson Button (Britain) Honda 1 lap
11. Christijan Albers (Netherlands) MF1 - Toyota 1 lap
13. Yuji Ide (Japan) Super Aguri - Honda 3 laps r. Juan Pablo Montoya [ Images ] (Colombia) McLaren 11 laps r. Tiago Monteiro (Portugal) MF1 - Toyota 18 laps r. Vitantonio Liuzzi (Italy) Toro Rosso - Cosworth 20 laps r. Michael Schumacher (Germany) Ferrari 25 laps r. Mark Webber [ Images ] (Australia [ Images ]) Williams - Cosworth 35 laps r. Christian Klien (Austria) RedBull - Ferrari 53 laps r. Jarno Trulli [ Images ] (Italy) Toyota 57 laps r. Nico Rosberg [ Images ] (Germany) Williams - Cosworth 57 laps r. Felipe Massa [ Images ] (Brazil) Ferrari 57 laps
(rank: r = retired, nc = not classified)
Fastest Lap: Kimi Raikkonen, 1:26.045, lap 57.