:1945 U.S. National Championships (tennis)

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{{Use American English|date=July 2023}}

{{TennisEventInfo|1945|U.S. National Championships|

| date = August 28 – September 3

| edition = 65th

| category = Grand Slam (ILTF)

| location = Forest Hills, Queens
New York City, New York

| venue=West Side Tennis Club

| surface = Grass

| champms={{flagicon|USA|1912}} Frank Parker

| champws={{flagicon|USA|1912}} Sarah Palfrey Cooke

| champmd={{flagicon|USA|1912}} Gardnar Mulloy / {{flagicon|USA|1912}} Bill Talbert

| champwd={{flagicon|USA|1912}} Louise Brough / {{flagicon|USA|1912}} Margaret Osborne

| champxd={{flagicon|USA|1912}} Margaret Osborne / {{flagicon|USA|1912}} Bill Talbert

}}

The 1945 U.S. National Championships (now known as the US Open) was a tennis tournament that took place on the outdoor grass courts at the West Side Tennis Club, Forest Hills in New York City, New York. The tournament ran from August 28 until September 3. It was the 65th staging of the U.S. National Championships, and due to World War II it was the only Grand Slam tennis event of the year.{{cite book|last=Collins|first=Bud|title=The Bud Collins History of Tennis|year=2010|publisher=New Chapter Press|location=[New York]|isbn=978-0942257700|edition=2nd|pages=77–78}}