Lichens are well known combination of an alga and a fungus where fungus has :-

A lichen is a symbiotic association (mutualism) between an alga (phycobiont) and a fungus (mycobiont).
The algal partner is autotrophic and prepares food by photosynthesis for both.
The fungal partner provides shelter, absorbs water and minerals and protects the alga from drying.
Both partners benefit, and they are so closely associated that the lichen looks like a single organism.
So in a lichen the fungus has a symbiotic relationship with the alga. (Lichens are good indicators of air pollution, as they do not grow in polluted areas.)