Townsend's round of 64, which included six birdies and a chip-in eagle, was achieved with a new set of irons after his own were stolen. It was his best of the season.
Colin Montgomerie, of Scotland, hit a nine-birdie 65 to finish with a group one shot behind.
'I've got to be very pleased with that start,' Montgomerie, who is still seeking his first win of 1992 despite a series of top-four finishes, said.
'I shot nine birdies to win the pro-am here with a 64 and made the same number today. That's a birdie every second hole and no one can complain about that sort of average in such warm conditions and with the greens getting spiked up.
'I'm giving myself so many birdie chances because my irons are superb at the moment. I made one 20-footer and the other birdies were from 10 feet or less.'
Montgomerie declined to wear any headgear in an attempt to become accustomed to the sort of heat he will face in America next week for the USPGA in St Louis.
'It's good practice, although it will be a lot warmer there,' he said. 'I'm knackered and suffering from a headache, but the heat doesn't worry me. My stamina is good and I've plenty of energy.'
BMW INTERNATIONAL OPEN TOURNAMENT (Munich) First-round scores (GB or Irl unless stated): 64 J Townsend (US). 65 C Rocca (It), O Sellberg (Swe), T Levet (Fr), C Montgomerie, J Quiros (Sp). 66 P Azinger (US), B Langer (Ger), M Martin (Sp), G Day (US), M Mackenzie, O Nordberg (Swe), D Feherty, A Mednick (Swe), P Walton, R Lee, G Ralph. 67 F Lindgren (Swe), B Ogle (Aus), D Gilford, P Fowler (Aus), S Grappasonni (It), R Claydon, R McFarlane, I Palmer (SA), D Mijovic (Can), W Riley (Aus), S Richardson, R Hartmann (US), I Spencer. 68 S Hamill, A Sorensen (Den), F Nobilo (NZ), P Stewart (US), A Forsbrand (Swe), J Spence, P Teravainen (US), D Clarke, D Silva (Por), P Senior (Aus), R Belhorst (Ger), M Clayton (Aus), J Carriles (Sp), B Marchbank, D Cooper, R Chapman. 69 L White, K Trimble (Aus), B Malley (US), J van de Velde (Fr), J Carter (US), G Brand Jnr, A Cejka (Ger), J Rutledge (Can), D J Russell, H-P Thuel (Ger), M James, A Hare, *K Dietrich (Ger), D Curry, D Williams, A Sherborne, J Payne, M Jiminez (Sp), G J Brand, T Geogele (Ger), T Gideon (Ger), W John (Ger). 70 C Williams, G Turner, R Postiglione (Ger), C van der Velde (Hol), R Rafferty, G Levenson (SA), S McAllister, R Kawigishi (Jap), R Davis (Aus), P Haugsrud (Nor), S Tinning (Den), E Giraud (Fr), S Lyle, H Baiocchi (SA), M Miller, M Moreno (Sp), S Bennett, S Luna (Sp), K Dickens. 71 M Farry (Fr), J O'Flynn, S Simpson (US), M Lanner (Swe), R Mund (Ger), C Pavin (US), O Vincent III (US), D Love III (US), R Winchester, R Boxall, C Platts, A Postiglione (Ger), J Metcalfe, C Moody. Selected: 72 M Sunesson (Swe). 74 M Roe, C O'Connor Jnr. Retired: B Barnes. *amateurReuse content