Combined combustion and pyrolysis (CCP) systems, and associated systems and methods, are disclosed herein. In some embodiments, the CCP system includes an input valve fluidly coupleable to a fuel supply to receive a hydrocarbon reactant, a CCP reactor fluidly coupled to the input valve, and a carbon separation component fluidly coupled to the CCP reactor. The CCP reactor can include a combustion chamber, a reaction chamber in thermal communication with the combustion chamber and/or fluidly coupled to the input valve, and an insulating material positioned to reduce heat loss from the combustion chamber and/or the reaction chamber. The CCP reactor can also include a combustion component positioned to combust a fuel within the combustion chamber. The combustion can heat the reaction chamber and the hydrocarbon reactant flowing therethrough. The heat causes a pyrolysis of the hydrocarbon reactant that generates hydrogen gas and carbon.