Uppu Aru Lagoon

{{Infobox lake

| name = Uppu Aru Lagoon

| image =

| caption =

| image_bathymetry =

| pushpin_map = Sri Lanka Northern Province#Sri Lanka

| caption_bathymetry=

| location = Jaffna District, Sri Lanka

| coords = {{coord|9|41|N|80|05|E|region:LK_type:waterbody|display=inline,title}}

| type = Lagoon

| inflow =

| outflow = Jaffna Lagoon

| catchment =

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| length =

| width =

| area = {{convert|30|km2|sqmi|sp=us}}

| depth =

| max-depth = {{convert|3|m|ft|sp=us}}

| volume =

| residence_time =

| shore =

| elevation = Sea level

| frozen =

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}}

Uppu Aru lagoon is a lagoon in Jaffna District, northern Sri Lanka. The lagoon separates the Valikamam region from the Thenmarachchi region.

The lagoon is linked to Jaffna Lagoon by a short channel to the south. The lagoon's water is brackish.{{cn|date=July 2023}}

The lagoon is surrounded by a densely populated region containing palmyra palms, coconut plantations, grassland, rice paddies and extensive vegetable gardens.{{cn|date=July 2023}}

The lagoon has extensive mudflats and salt marshes. It is surrounded by mangroves, particularly Avicennia. The lagoon attracts a wide variety of water birds including American flamingoes, ducks, garganey, black-tailed godwit and other shorebirds.{{cn|date=July 2023}}