You can find wood blewits (Lepista nuda) in broad-leaved woodlands at just about any time of year, it also crops up in gardens (especially compost heaps) and in hedgerows too. It is widespread and very common but also a bit variable and can be mistaken for similar toadstools. More likely, of course, the similar but rarer species are likely to be dismissed as this one!
This species has a lilac coloured stem but that is not always visible without destroying the fungus as it is hidden under the large cap which can be as much as 10cm across. Said to be good to eat but it causes 'adverse reactions' in some people - want to give it a miss? I would!