Yes, if one leg of a single booking (one PNR) is cancelled by the airline, you are generally entitled to a full refund for the entire ticket, including the return flight or any connecting legs you haven't flown yet. Under 2026 regulations (like UK/EU 261 and new DOT rules in the US), if the airline cannot provide a suitable alternative flight that gets you to your destination within a reasonable window, they must offer you a choice between re-routing or a full cash refund. If you are in the middle of a journey and a connecting leg is cancelled, the airline must also provide a "flight back to your original point of departure" at no cost if the cancellation makes your trip redundant. This protection only applies to "linked" tickets; if you booked separate "point-to-point" tickets on different airlines, a cancellation on one will not legally entitle you to a refund on the other.