There is provided a heat exchanger comprising: a conduit defining an inlet flow path for a fluid; a header disposed to receive a flow from the inlet flow path; a heat exchanger matrix disposed to receive a flow from the header; and a swirler disposed within the conduit and the header. The swirler is arranged to disperse a flow from the inlet flow path over the heat exchanger matrix. The conduit, header, and swirler are formed as a unitary piece by additive manufacturing.