The most experienced and intriguing driver line-up is at McLaren where former world champions Fernando Alonso and Jenson Button have started 500 grands prix between them.
In contrast, Toro Rosso's Max Verstappen and Carlos Sainz Jr have yet to start an F1 race.
It will be Button's 16th season in F1, making him the most experienced driver on the grid.
At 35, 2007 world champion Kimi Raikkonen will be the oldest, while Dutchman Verstappen, 17, is the youngest.
Ferrari's Sebastian Vettel has the most wins of any driver on the grid with 39, six clear of Hamilton.
Here, BBC Sport profiles the 18 drivers set to contest the 2015 F1 season and chief F1 writer Andrew Benson gives his assessment.