The CFA said there were more than 20 grass and scrub fires across regional Victoria that started around 8pm yesterday.
One fire, at Hillcrest, 150 kilometres west of Melbourne, grew 100 metres in length and 50 metres in height, taking an hour for firefighters to bring under control.
The band of lightning swept through from the west of the state yesterday evening, displaying spectacular lightning shows across Melbourne and the rest of the state.
While most of the fires caused were small and easy for firefighters to extinguish, the fire on the Smitesdale-Snake Valley Road, at Hillcrest, quickly grew in size.
The fire was sparked by lightning shortly before 5am and burnt through stringy bark bushland, prompting nine fire trucks to rush to the scene.
The fire was brought under control after 5.30am and eventually declared safe by 7am.
Right across Melbourne, residents captured the spectacular lightning shows.
Flashes of lightning were filmed lightning up the sky over housing estates, beaches and freeways.
The SES responded to 69 calls for help overnight.
The CFA said more small grass fires were expected to be discovered throughout today.