# Swimming at the 1948 Summer Olympics – Men's 100 metre backstroke

The men's 100 metre backstroke event at the 1948 Olympic Games took place between 4 and 6 August, at the Empire Pool. This swimming event used the backstroke. Because an Olympic-size swimming pool is 50 metres long, this race consisted of two lengths of the pool.

## Medalists

| Gold | Allen Stack United States |
| Silver | Bob Cowell United States |
| Bronze | Georges Vallerey France |

## Results
### Heats

The fastest two in each heat and the four fastest third-placed from across the heats advanced.
Heat 1
| Place | Swimmer | Time | Qual. |
| 1 | Jackie Wiid (RSA) | 1:08.5 | QQ |
| 2 | Kees Kievit (NED) | 1:10.8 | QQ |
| 3 | José Vegazzi (ARG) | 1:13.8 | |
| 4 | Francisco Calamita (ESP) | 1:14.2 | |
| 5 | Eric Jubb (CAN) | 1:14.3 | |
| 6 | Per-Olof Olsson (SWE) | 1:14.6 | |
| 7 | Khamlillal Shah (IND) | 1:19.9 | |
Heat 2
| Place | Swimmer | Time | Qual. |
| 1 | Bruce Bourke (AUS) | 1:11.3 | QQ |
| 2 | Ilo da Fonseca (BRA) | 1:11.9 | QQ |
| 3 | Jiří Kovář (TCH) | 1:12.9 | |
| 4 | Carlos Noriega (URU) | 1:15.0 | |
| 5 | Martin Lundén (SWE) | 1:15.6 | |
| 6 | Tonatiuh Gutiérrez (MEX) | 1:15.6 | |
| 7 | Jaffar Ali Shah (PAK) | 1:30.2 | |
Heat 3
| Place | Swimmer | Time | Qual. |
| 1 | John Brockaway (GBR) | 1:09.2 | QQ |
| 2 | Mario Chávez (ARG) | 1:09.7 | QQ |
| 3 | Clemente Mejía (MEX) | 1:09.8 | qq |
| 4 | Lucien Zins (FRA) | 1:10.9 | qq |
| 5 | Mário Simas (POR) | 1:12.8 | |
| 6 | Fritz Zwazl (AUT) | 1:13.5 | |
| 7 | Nikolaos Melanofeidis (GRE) | 1:22.0 | |
Heat 4
| Place | Swimmer | Time | Qual. |
| 1 | Allen Stack (USA) | 1:06.6 | QQ |
| 2 | Bert Kinnear (GBR) | 1:09.7 | QQ |
| 3 | Paulo Silva (BRA) | 1:10.0 | qq |
| 4 | Tony Summers (GBR) | 1:11.2 | |
| 5 | Gyula Válent (HUN) | 1:11.8 | |
| 6 | Manuel Guerra (AUT) | 1:14.8 | |
| 7 | Prahtip Mitra (IND) | 1:24.5 | |
Heat 5
| Place | Swimmer | Time | Qual. |
| 1 | Bob Cowell (USA) | 1:06.9 | QQ |
| 2 | René Pirolley (FRA) | 1:11.4 | QQ |
| 3 | Donald Shanks (BER) | 1:17.1 | |
| 4 | Dorri El-Said (EGY) | 1:19.0 | |
| 5 | Guðmundur Ingólfsson (ISL) | 1:19.4 | |
Heat 6
| Place | Swimmer | Time | Qual. |
| 1 | Georges Vallerey, Jr. (FRA) | 1:07.4 | QQ |
| 2 | Howard Patterson (USA) | 1:09.3 | QQ |
| 3 | Hélio Silva (BRA) | 1:10.5 | qq |
| 4 | Federico Neumayer (ARG) | 1:10.8 | |
| 5 | Peter Mingie (CAN) | 1:13.2 | |
| 6 | Hans Blumer (SUI) | 1:18.5 | |

### Semifinals

The fastest three in each semi-final and the fastest from across the semi-finals advanced.
Semifinal 1
| Place | Swimmer | Time | Qual. |
| 1 | Allen Stack (USA) | 1:07.3 | QQ |
| 2 | Georges Vallerey, Jr. (FRA) | 1:08.3 | QQ |
| 3 | John Brockaway (GBR) | 1:09.1 | QQ |
| 4 | Clemente Mejía (MEX) | 1:09.6 | qq |
| 5 | Mario Chávez (ARG) | 1:09.8 | qq |
| 6 | Paulo Silva (BRA) | 1:09.8 | |
| 7 | Kees Kievit (NED) | 1:11.3 | |
| 8 | Bruce Bourke (AUS) | 1:11.4 | |
Semifinal 2
| Place | Swimmer | Time | Qual. |
| 1 | Bob Cowell (USA) | 1:08.5 | QQ |
| 2 | Bert Kinnear (GBR) | 1:09.2 | QQ |
| 3 | Jackie Wiid (RSA) | 1:09.2 | QQ |
| 4 | Howard Patterson (USA) | 1:09.9 | |
| 5 | Hélio Silva (BRA) | 1:10.1 | |
| 6 | Lucien Zins (FRA) | 1:11.5 | |
| 7 | Ilo da Fonseca (BRA) | 1:11.6 | |
| 8 | René Pirolley (FRA) | 1:12.9 | |
Key: Q = qualification by place in heat, q = qualification by overall place

### Final

| Rank | Athlete | Country | Time |
| | Allen Stack | United States | 1:06.4 |
| | Bob Cowell | United States | 1:06.5 |
| | Georges Vallerey | France | 1:07.8 |
| 4 | Mario Chávez | Argentina | 1:09.0 |
| 4 | Clemente Mejía | Mexico | 1:09.0 |
| 6 | Jackie Wiid | South Africa | 1:09.1 |
| 7 | John Brockway | Great Britain | 1:09.2 |
| 8 | Bert Kinnear | Great Britain | 1:09.6 |