The 68-year-old from Bournemouth died when his Vauxhall Astra hit a Nissan Juke on the A31 near Corfe Mullen.
The road, near the Coventry Arms pub, was closed for more than five hours after the crash happened at 13:20 BST.
The driver of the Nissan, a 49-year-old woman from Waterlooville, was seriously injured and airlifted to Southampton General Hospital but police said her condition was not life-threatening.
Three men who were travelling in the Nissan sustained serious but not life-threatening injuries and were taken to Poole Hospital.
Sgt Mark Scammell said: "I would like to thank motorists for their patience during the road closures which are necessary to allow emergency services to deal with the incident."

The deal will see the firm taken over by holding company Cheil Industries, another part of the Samsung group.
The merger is strongly opposed by some of Samsung C&T's shareholders, led by US hedge fund Elliott Associates.
For Samsung's founding family, the move is a crucial step in consolidating control of the conglomerate.
Shareholders in Cheil Industries approved the merger earlier on Friday.
Shares in Samsung C&T fell 10.4% and Cheil Industries dropped 7.7% after the merger was approved.
Elliott Associates, which is the second largest single shareholder in C&T, says the takeover significantly undervalues the company's stock.
The hedge fund had filed several unsuccessful law suits to stop the vote from going ahead.
The takeover is key to consolidating the Samsung founding family's control of the multi-headed conglomerate.
It is of particular significance as it comes ahead of a generational power transfer at Samsung.
The business empire's patriarch Lee Kun-hee has been in hospital since May 2014 and his son Lee Jae-yong is to take a bigger leadership role.

PwC's Northern Ireland economic outlook said this was despite overall unemployment having fallen by more than 10,000 since June 2014.
It said poor productivity remains the single biggest challenge to Northern Ireland's sustained recovery.
PwC's Esmond Birnie said the pace of recovery was "decelerating".
"Over the past seven months business confidence has been mixed, sometimes negative but always lagging the GB regions," Mr Birnie, who is PwC's chief economist in Northern Ireland, said.
"There have also been recent mixed messages around consumer confidence, with June 2015 seeing the first rise in unemployment for more than two years; this may simply be a blip - or it may be indicative of a deeper malaise.
"Currently, Northern Ireland's output is still 8% below the pre-crisis peak of 2008 and is something of a two-speed economy with employment contracting in public sector and financial services but growing fairly rapidly in advanced manufacturing, pharma, food processing and tourism.
"PwC forecasts that Northern Ireland's economic growth will remain the lowest of the 12 UK regions at around 1.8% in 2015 - lower than the 2.2% growth experienced in 2014 - and will fall again in 2016 to around 1.7%."
The report said that Northern Ireland's unemployment claimant count increased by 200 between May and June, the first month-on-month increase since December 2008.
It said that 62% of those registered as unemployed have been out of work for more than 12 months, while 19.7% of young people aged 18-25 are unemployed - well above the UK average of 13.2%.
PwC said the recent budget "confirmed that welfare reform and austerity will continue and that Northern Ireland probably faces a further four years of challenging economic circumstances, particularly around public spending".
A man has died in a crash involving two cars on one of Dorset's busiest routes.
[NEXT_CONCEPT]
One of South Korea's most controversial mergers has been given approval by shareholders of the construction company Samsung C&T.
[NEXT_CONCEPT]
Northern Ireland's economic growth will remain the lowest of the 12 UK regions in 2015, a new report has said.