The Briton capitalised on a crash at the start involving title rival Sebastian Vettel, the German's Ferrari teammate Kimi Raikkonen and the Red Bull Racing auto of Max Verstappen, which eliminated all three men, to win at the Marina Bay Circuit for a third time.
Rain at the Marina Bay street circuit in the hours before lights out raised the possibility of the first wet Singapore race in its 10-year history.
But Hamilton dodged the pile-up and he progressed from fifth on the grid to first, ahead of Ricciardo, as the race finally restarted after a safety vehicle.
Ferrari blamed Verstappen, while Red Bull team boss Christian Horner said the 19-year-old was a victim "of somebody else's accident".
But Verstappen had Raikkonen, who had made a fast getaway from fourth, alongside him, and the pair made contact.
Raikkonen lost control of his vehicle and collected Verstappen as he slid uncontrollably into Turn 1, causing irreparable damage to both cars and forcing them out of the race immediately.
Alonso lasted just a few laps before the damage sustained at the first corner forced him to retire, and Toro Rosso's Daniil Kvyat became the fifth man out when he ploughed nose-first into a barrier - prompting a second safety auto. However, on the exit of Turn 2 he lost control of his auto, spinning into the wall and out of the race.
Mercedes driver Lewis Hamilton drives out of the pit lane during Friday practice for the Singapore Grand Prix
The FIA stewards announced that the startline incident was under investigation, with a ruling expected after the race.
"I don't know [what happened], I didn't see that much". Max is next to me, so first of all I guess I'm racing him and then Daniel (Ricciardo) and so on and so forth.
"That's how this business is, and we'll move on". It doesn't change much.
"But we didn't have the pace we showed on Friday, we struggled to look after the tyres - when able to punch out a good laptime, I couldn't maintain it, whereas Lewis could answer and answer again".
Having built on that advantage, championship leader Hamilton was frustrated by the reappearance of the safety auto on lap 11 when Daniil Kvyat drove into the barriers.
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