Lysekil has no railway. The nearest mainline station is Uddevalla, 35 km east; from there the regional bus (line 841) takes about an hour to Lysekil and runs roughly hourly. Uddevalla is 70 minutes by train from Gothenburg Central, so the full trip from Gothenburg takes about two and a half hours by public transport.
By car the drive from Gothenburg is around two hours on the E6 and Route 161, through pleasant rolling farmland and pine forest with occasional glimpses of the sea. From Oslo reckon three to three and a half hours. Approaching from the south, the free car ferry from Fiskebäckskil — a short, beautiful five-minute crossing — saves you the long road around the Gullmar fjord.