Also known as Diogenes of Sinope (his birthplace, which he left under somewhat of a shadow), he was the ancient Greek philosopher who founded Cynicism. (413-321 BCE)
 
Known for his ascetic lifestyle and radical criticism and rejection of social conventions, he advocated a return to nature, the renunciation of wealth, and proclaimed himself a 'kosmopolites', a 'citizen of the world'!
 
Dividing his time between Athens and Corinth, he embraced a life of poverty and self-sufficiency, famous for his unconventional, shameless behaviours that openly challenged the norms of society.
 
Diogenes made a distinction between actual poverty (being economically poor) and the feeling of poverty (suffering from chronic dissatisfaction due to unmet social expectations). 
 
He lived in a large pithos (a ceramic jar usually meant for storing foodstuffs), and wandered about barefoot, dishevelled, and scantily clad with a lit lantern in broad daylight, claiming to be 'looking for a (wise) man - sophos'. In vain!
 
Emulating Socrates, Diogenes publicly questioned those who claimed to possess wisdom (sophia), and he preferred to engage people in their everyday lives rather than teaching in formal educational settings, as other philosophers did.
 
This quotation is attributed to him:
'Let the whole world be large enough for me, let me call the universe my home.'