Horse transport causes significant welfare stress, with physiological indicators including elevated cortisol, increased heart rate, dehydration, and gastric ulcer development on longer journeys. Horses are transported for competition, sale, breeding, slaughter, and relocation - with welfare implications varying by journey duration, vehicle design, density, and management. Research demonstrates horses prefer to travel facing backwards (reducing balance effort and muscle fatigue) though forward-facing transport is standard in most trailers. Journey durations above 8 hours significantly increase stress indicators; EU regulations limit journey times for horses being transported for slaughter. Lairage rest requirements (24 hours after 24 hours of transport) are scientifically supported. Long-distance international horse transport by air presents welfare challenges including dehydration, pleuropneumonia, and myopathy from restricted movement. Welfare improvements include appropriate feed and water provision, familiar companions, and regular veterinary monitoring on long journeys.