The youngest of the three Castiglioni brothers, Achille Castiglioni (Milan, 1918 - 2002) was among the most influential architects, designers and academics on the Italian and international scene. After obtaining his degree in architecture in 1944 at the Milan Polytechnic, he began working in the office previously founded by his brothers Livio and Pier Giacomo. When, in 1953, Livio decided to pursue an independent career, the office was taken over by the close-knit brothers, Achille and Pier Giacomo. They made their debut creating installations for the exhibition spaces of companies like RAI, Montecatini and Eni, working with such figures as Bruno Munari and Max Huber, and experimenting with innovative solutions, especially lighting technology. At the same time, they developed their architectural practice, with the construction of such watershed buildings as the Palazzo della Permanente (1952), the parish church S. Gabriele Arcangelo in Mater Dei (1956), the headquarters of the Chamber of Commerce (1958).
The Castiglioni brothers presented a series of objects representing their language that combined function and minimalism using anonymous objects in an ironic key during the exhibitions "Forme e Colori nella casa d'Oggi" (Form and Colour in Today's Homes) (Villa Olmo, Como, 1957) and "La Casa Abitata" (The Inhabited House) (Florence, 1965). These included the Sella and Mezzadro stools, today produced by Zanotta; the Cubo armchair, today in the Meritalia collection by Arflex; the Luminator lamp, now manufactured by Flos, and awarded the Compasso d'Oro in 1955; the Firenze wall clock (Alessi); the Tric folding chair. With his brother, Achille established himself as one of the most influential Italian designers, going on to become one of the founding members of the Association for Industrial Design (ADI) and one of the organisers of the Compasso d'Oro award. He won the prize eight times - for the Luminator lamp, the Palini T12 chair (1960), the Pitagora coffee machine for LaCimbali (1962), the Spinamatic beer tap for Poretti (1964), and the simultaneous translation headset for Phoebus Alter (1967), always with his brother Pier Giacomo. They also won awards for the Parentesi lamp for Flos (1979), for the Omsa hospital bed (1979), the Dry cutlery for Alessi (1984), as well as numerous honourable mentions.
In almost 60 years of activity, Achille Castiglioni created over one hundred objects, some included in the permanent collections of MoMA in New York and other important museums. He undoubtedly contributed to revolutionising design and diffusing made-in-Italy values. He worked for such prestigious brands as Alessi, Kartell, Flos, Zanotta, De Padova, Poltrona Frau, Siemens, Brionvega, just to name a few. Achille Castiglioni died in 2002 at the age of 84 in his studio in Piazza Castello, Milan, transformed into the Studio Museo Achille Castiglioni in 2005.