| Grand Prix: | Nations |
| Flag: | Italy |
| Location: | Autodromo Nazionale Monza |
| Course Mi: | 3.91 |
| Course Km: | 6.30 |
| Race No: | 6 |
| Season No: | 6 |
| Date: | 4 September |
| Year: | 1949 |
| Fast Rider 500: | Nello Pagani |
| Fast Rider 500 Country: | Italy |
| Fast Rider 500 Bike: | Gilera |
| First Rider 500: | Nello Pagani |
| First Rider 500 Country: | Italy |
| First Rider 500 Bike: | Gilera |
| Second Rider 500: | Arciso Artesiani |
| Second Rider 500 Country: | Italy |
| Second Rider 500 Bike: | Gilera |
| Third Rider 500: | Bill Doran |
| Third Rider 500 Country: | UK |
| Third Rider 500 Bike: | AJS |
| Fast Rider 250: | Dario Ambrosini |
| Fast Rider 250 Country: | Italy |
| Fast Rider 250 Bike: | Benelli |
| First Rider 250: | Dario Ambrosini |
| First Rider 250 Country: | Italy |
| First Rider 250 Bike: | Benelli |
| Second Rider 250: | Gianni Leoni |
| Second Rider 250 Country: | Italy |
| Second Rider 250 Bike: | Moto Guzzi |
| Third Rider 250: | Umberto Masetti |
| Third Rider 250 Country: | Italy |
| Third Rider 250 Bike: | Benelli |
| Fast Rider 125: | Gianni Leoni |
| Fast Rider 125 Country: | Italy |
| Fast Rider 125 Bike: | FB-Mondial |
| First Rider 125: | Gianni Leoni |
| First Rider 125 Country: | Italy |
| First Rider 125 Bike: | FB-Mondial |
| Second Rider 125: | Umberto Masetti |
| Second Rider 125 Country: | Italy |
| Second Rider 125 Bike: | Moto Morini |
| Third Rider 125: | Umberto Braga |
| Third Rider 125 Country: | Italy |
| Third Rider 125 Bike: | FB-Mondial |
| Fast Rider Sidecar: | Eric Oliver |
| Fast Rider Sidecar Country: | UK |
| Fast Rider Sidecar Bike: | Norton |
| Fast Passenger Sidecar: | Denis Jenkinson |
| Fast Passenger Sidecar Country: | UK |
| Fast Time Sidecar: | 86.7mph |
| First Rider Sidecar: | Ercole Frigerio |
| First Rider Sidecar Country: | Italy |
| First Passenger Sidecar: | Lorenzo Dobelli |
| First Passenger Sidecar Country: | Italy |
| First Rider Sidecar Bike: | Gilera |
| Second Rider Sidecar: | Frans Vanderschrick |
| Second Rider Sidecar Country: | Belgium |
| Second Passenger Sidecar: | Martin Whitney |
| Second Passenger Sidecar Country: | United Kingdom |
| Second Rider Sidecar Bike: | Norton |
| Third Rider Sidecar: | Albino Milani |
| Third Rider Sidecar Country: | Italy |
| Third Passenger Sidecar: | Ezio Ricotti |
| Third Passenger Sidecar Country: | Italy |
| Third Rider Sidecar Bike: | Gilera |
The 1949 Nations Grand Prix was the fifth round of the 1949 Grand Prix motorcycle racing season. It took place at the Autodromo Nazionale Monza.
Italian rider Nello Pagani won the 500 cc race riding a Gilera from Arciso Artesiani and Bill Doran.
Despite Dario Ambrosini winning the 250 cc race, a fourth-place finish for Italian Moto Guzzi rider Bruno Ruffo was enough for him to win the 250 cc championship, the only championship in the first season with results close enough to be still in doubt at the final race.
| Pos | Rider | Manufacturer | Time | Points | |
|---|---|---|---|---|---|
| 1 |  Nello Pagani | Gilera | 1:16:36.8 | 11 | |
| 2 | Arciso Artesiani | Gilera | +0.8 | 8 | |
| 3 |  Bill Doran | AJS | +15.8 | 7 | |
| 4 | Guido Leoni | Moto Guzzi | +18.2 | 6 | |
| 5 | Bruno Bertacchini | Moto Guzzi | +31.2 | 6 | |
| 6 |  Reg Armstrong | AJS | +1:03.6 | ||
| 15 finishers | |||||
| [1] [2] | |||||
| Pos | Rider | Manufacturer | Time | Points | |
|---|---|---|---|---|---|
| 1 | Dario Ambrosini | Benelli | 1:02:53.8 | 11 | |
| 2 | Gianni Leoni | Moto Guzzi | +32.6 | 8 | |
| 3 | Umberto Masetti | Benelli | +52.2 | 7 | |
| 4 | Bruno Ruffo | Moto Guzzi | 6 | ||
| 5 | Claudio Mastellari | Moto Guzzi | 5 | ||
| 6 | Bruno Francisci | Moto Guzzi | |||
| [3] | |||||
| Pos | Rider | Manufacturer | Points | |
|---|---|---|---|---|
| 1 | Gianni Leoni | FB-Mondial | 11 | |
| 2 | Umberto Masetti | Moto Morini | 8 | |
| 3 | Umberto Braga | FB-Mondial | 7 | |
| 4 | Renato Magi | Moto Morini | 6 | |
| 5 | Nello Pagani | FB-Mondial | 5 | |