The 22-year old, who was part of Spain's European Under-21 Championship-winning side this summer, featured 25 times in La Liga last season, finding the net on four occasions.
Vazquez makes the move to the Liberty Stadium with a view to a permanent transfer and manager Michael Laudrup says that the youngster will offer his side an attacking alternative.
"Vasquez is a young player I know from his time at Espanyol and now Getafe," he told the Swans' official website.
"He is a little different to the strikers we have and has the characteristics we have been looking for. He will give us a different option."
Vazquez becomes Swansea's 11th signing this summer and chairman Huw Jenkins also talked up the abilities of their latest arrival.
"He is a young player with plenty of potential. He has already done well out in Spain and looks like the right signing for us at this stage," said Jenkins.