Rattlesnake River

{{Use American English|date=February 2025}}

{{Infobox river

| name = Rattlesnake River

| name_native =

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| pushpin_map = New Hampshire#USA

| pushpin_map_size = 250 px

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| subdivision_type1 = Country

| subdivision_name1 = United States

| subdivision_type2 = State

| subdivision_name2 = New Hampshire

| subdivision_type3 = County

| subdivision_name3 = Strafford

| subdivision_type4 = Towns

| subdivision_name4 = Farmington

| subdivision_type5 =

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| length = {{convert|3.6|mi|km|abbr=on}}

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| source1 =

| source1_location = Farmington

| source1_coordinates= {{coord|43|21|25|N|71|4|50|W|type:river|display=inline}}

| source1_elevation = {{convert|710|ft|abbr=on}}

| mouth = Cocheco River

| mouth_location = Farmington

| mouth_coordinates = {{coord|43|21|59|N|71|2|10|W|type:river|display=inline,title}}

| mouth_elevation = {{convert|238|ft|abbr=on}}

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The Rattlesnake River is a {{convert|3.6|mi|km|adj=mid|-long}}[http://www.granit.unh.edu New Hampshire GRANIT state geographic information system] river in eastern New Hampshire in the United States. It is a tributary of the Cocheco River, part of the Piscataqua River watershed leading to the Atlantic Ocean.

The river is located entirely in the town of Farmington. It rises north of Hussey Mountain and Chesley Mountain and flows east to the Cocheco, dropping nearly {{convert|500|ft}} in elevation over its length.