As well as retaining his world number one ranking, Norfolk's victory takes his tally of wheelchair tennis majors to 17, while he has now won 41 career singles titles since 2001.
The 49-year-old two-time Paralympic champion opened the final with a love service game and went on to take a 4-1 lead after Wagner converted his one and only break point of the first set to take the second game.
Norfolk took the American to deuce in three of Wagner's four service games and the Hampshire player converted his first set point for his third break of the opening set.
Wagner took a toilet break at 2-1 in the second set and although Norfolk won the next game to secure the first break of the second set he appeared to tighten up as Wagner put together a sequence of four games to lead 5-3.
However, with the prospect of losing a second set to Wagner for the second time in three days, Norfolk's ability to perform under pressure then came to the fore and he started to play more relaxed tennis and subsequently came back to force a tie-break.
Norfolk opened a 4-1 lead in the tie-break, but a double-fault allowed Wagner to level at 4-4.
That was to be Wagner's only remaining success and Norfolk reeled off the next three points to win his third successive Australian Open title and his fourth since 2004 after an 96 minutes of play.
Norfolk said: "It's a great achievement to win my fourth Aussie Open and I am really happy with today's win, the way my team has worked this week and to be in the sunshine, not the snow."
"I love repeats and to do it in straight sets is very satisfying.
"I hope to have set the stage for Andy Murray tomorrow.
"It's nice to consolidate my number one world ranking this early in the season, especially with the support I have had this week from Andy Murray, his mum and Team Murray, not to mention the support from [Lawn Tennis Association chief executive] Roger Draper, who watched every one of my matches."
January 2010: British pair reached Australian Open finals
January 2010: Norfolk begins chase for Australian Open title