Great Western Railway operates a train from Bristol to Merthyr Tydfil hourly. Tickets cost $21 - $40 and the journey takes 44 min. Alternatively, Megabus UK operates a bus from Bristol to Merthyr Tydfil every 4 hours. Tickets cost $18 - $24 and the journey takes 1 h 15 min.
From Bristol Temple Meads train to Cardiff Central then train to Merthyr Tydfil. 2 h 9 min £27. From Broadmead, Cabot Circus bus to Cardiff, Kingsway (Cardiff Castle) then bus to Merthyr Tydfil, Bus Station (Merthyr Tydfil Bus Station). 2 h 20 min £23. From Bristol City Centre, The Centre bus to Bristol International Airport, Airport Terminal, bus to Cardiff, Castle Stop KA (Cardiff Castle), then bus to Merthyr Tydfil, Bus Station (Merthyr Tydfil Bus Station). 3 h 33 min £24. From Bristol drive to Merthyr Tydfil. 1 h 9 min £11.