River Fynn

{{Infobox river

| name = Fynn

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| pushpin_map = United Kingdom Suffolk

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| pushpin_map_caption= Location of the river mouth within Suffolk

| subdivision_type1 = Country

| subdivision_name1 = England

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| subdivision_type3 = Region

| subdivision_name3 = Suffolk

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| length = {{convert|13.622|km|mi|abbr=on}}{{cite web |title=Fynn {{!}} Catchment Data Explorer {{!}} Catchment Data Explorer |url=https://environment.data.gov.uk/catchment-planning/v/c3-plan/WaterBody/GB105035040330 |website=environment.data.gov.uk |publisher=Department for Environment Food & Rural Affairs |access-date=5 October 2023}}

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| source1 =

| source1_location = Witnesham

| source1_coordinates= {{coord|52.2799|1.3048|display=inline}}

| source1_elevation = {{convert|60|m|abbr=on}}

| mouth =

| mouth_location = Martlesham

| mouth_coordinates = {{coord|52.07667|1.295313|display=inline,title}}

| mouth_elevation = {{convert|0|m|abbr=on}}

| progression =

| river_system = River Deben

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| custom_label = Water Body ID

| custom_data = GB105035040330

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}}

The River Fynn is a waterway in Suffolk which joins the River Deben. Its source is to the north-west of the village of Witnesham and it joins the Deben south of Woodbridge, via Martlesham Creek.{{cite web |title=Fynn Valley Walk Route |url=http://www.gps-routes.co.uk/routes/home.nsf/RoutesLinksWalks/fynn-valley-walk-walking-route |website=www.gps-routes.co.uk |publisher=GPS Cycle and Walking Routes |access-date=5 October 2023 |language=en}}

Among its tributaries are the River Lark, whose sources are to the north of Grundisburgh, and an unnamed stream which flows east from a point north of the village of Kesgrave, through the grounds of Kesgrave Hall. Both join the Fynn to the west of Martlesham.

{{Commons}}