This is the first monograph to explore one of the most ambitious and idiosyncratic – yet largely unknown – private collections of twentieth-century Western art, and its complex, charismatic creator Theodor ‘Teto’ Ahrenberg (1912–89). Containing over 6,000 artworks, the collection featured key works by artists as distinguished and diverse as Matisse, Picasso, Chagall, Le Corbusier, Olle Bærtling, Mark Tobey, Enrico Baj, Tadeusz Kantor, Lucio Fontana, Christo, Jean Tinguely and Niki de Saint Phalle. Ahrenberg’s ever-renewing collection was shaped by his commitment to contemporary art, his dedication to young and marginalized artists, and the conviction he was not merely a collector but a ‘catalyst’ – one who facilitated exhibitions, collaborations and commissions, and who employed art as an instrument against conservatism and complacency. Ahrenberg was passionate about meeting the artists whose work he acquired, and he accordingly established long-term friendships that transcended the conventional artist-collector dynamic. Living with Matisse, Picasso and Christo draws on the wealth of personal correspondence between Ahrenberg and ‘his’ artists, and presents much previously unpublished visual material including artworks, photographs and architectural plans.