Yes. A ferrous metal is one that contains iron, and stainless steels are ferrous because iron is their main constituent - even in highly alloyed grades such as super duplex or super austenitic stainless steels. Non-ferrous metals, by contrast, contain little or no iron; examples include aluminium, copper, lead, tin and zinc.
Many of the nickel alloys we supply also contain iron, though most people would not consider them ferrous because iron is only a minor constituent.