diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4d0005431..08e00f627 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,7 +10,8 @@ Full list of differences found in [this compare](https://github.com/open-telemet
 
 ### Changed
 
-* Remove if no changes for this section before release.
+* Add `csharp_namespace` option to protos.
+  ([#399](https://github.com/open-telemetry/opentelemetry-proto/pull/399))
 
 ### Added
 
diff --git a/opentelemetry/proto/collector/logs/v1/logs_service.proto b/opentelemetry/proto/collector/logs/v1/logs_service.proto
index 71e90dd16..cc1162fd8 100644
--- a/opentelemetry/proto/collector/logs/v1/logs_service.proto
+++ b/opentelemetry/proto/collector/logs/v1/logs_service.proto
@@ -18,6 +18,7 @@ package opentelemetry.proto.collector.logs.v1;
 
 import "opentelemetry/proto/logs/v1/logs.proto";
 
+option csharp_namespace = "OpenTelemetry.Proto.Collector.Logs.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.collector.logs.v1";
 option java_outer_classname = "LogsServiceProto";
diff --git a/opentelemetry/proto/collector/metrics/v1/metrics_service.proto b/opentelemetry/proto/collector/metrics/v1/metrics_service.proto
index 9e9b710c4..a013d2e77 100644
--- a/opentelemetry/proto/collector/metrics/v1/metrics_service.proto
+++ b/opentelemetry/proto/collector/metrics/v1/metrics_service.proto
@@ -18,6 +18,7 @@ package opentelemetry.proto.collector.metrics.v1;
 
 import "opentelemetry/proto/metrics/v1/metrics.proto";
 
+option csharp_namespace = "OpenTelemetry.Proto.Collector.Metrics.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.collector.metrics.v1";
 option java_outer_classname = "MetricsServiceProto";
diff --git a/opentelemetry/proto/collector/trace/v1/trace_service.proto b/opentelemetry/proto/collector/trace/v1/trace_service.proto
index 41dbeef33..75d694294 100644
--- a/opentelemetry/proto/collector/trace/v1/trace_service.proto
+++ b/opentelemetry/proto/collector/trace/v1/trace_service.proto
@@ -18,6 +18,7 @@ package opentelemetry.proto.collector.trace.v1;
 
 import "opentelemetry/proto/trace/v1/trace.proto";
 
+option csharp_namespace = "OpenTelemetry.Proto.Collector.Trace.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.collector.trace.v1";
 option java_outer_classname = "TraceServiceProto";
diff --git a/opentelemetry/proto/common/v1/common.proto b/opentelemetry/proto/common/v1/common.proto
index afb57eb43..70f423370 100644
--- a/opentelemetry/proto/common/v1/common.proto
+++ b/opentelemetry/proto/common/v1/common.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package opentelemetry.proto.common.v1;
 
+option csharp_namespace = "OpenTelemetry.Proto.Common.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.common.v1";
 option java_outer_classname = "CommonProto";
diff --git a/opentelemetry/proto/logs/v1/logs.proto b/opentelemetry/proto/logs/v1/logs.proto
index c524a96c2..8ec201477 100644
--- a/opentelemetry/proto/logs/v1/logs.proto
+++ b/opentelemetry/proto/logs/v1/logs.proto
@@ -19,6 +19,7 @@ package opentelemetry.proto.logs.v1;
 import "opentelemetry/proto/common/v1/common.proto";
 import "opentelemetry/proto/resource/v1/resource.proto";
 
+option csharp_namespace = "OpenTelemetry.Proto.Logs.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.logs.v1";
 option java_outer_classname = "LogsProto";
diff --git a/opentelemetry/proto/metrics/v1/metrics.proto b/opentelemetry/proto/metrics/v1/metrics.proto
index 4a59f92a1..205e986e7 100644
--- a/opentelemetry/proto/metrics/v1/metrics.proto
+++ b/opentelemetry/proto/metrics/v1/metrics.proto
@@ -19,6 +19,7 @@ package opentelemetry.proto.metrics.v1;
 import "opentelemetry/proto/common/v1/common.proto";
 import "opentelemetry/proto/resource/v1/resource.proto";
 
+option csharp_namespace = "OpenTelemetry.Proto.Metrics.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.metrics.v1";
 option java_outer_classname = "MetricsProto";
diff --git a/opentelemetry/proto/resource/v1/resource.proto b/opentelemetry/proto/resource/v1/resource.proto
index 0a5473455..6637560bc 100644
--- a/opentelemetry/proto/resource/v1/resource.proto
+++ b/opentelemetry/proto/resource/v1/resource.proto
@@ -18,6 +18,7 @@ package opentelemetry.proto.resource.v1;
 
 import "opentelemetry/proto/common/v1/common.proto";
 
+option csharp_namespace = "OpenTelemetry.Proto.Resource.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.resource.v1";
 option java_outer_classname = "ResourceProto";
diff --git a/opentelemetry/proto/trace/v1/trace.proto b/opentelemetry/proto/trace/v1/trace.proto
index f2c13712b..1d840cd63 100644
--- a/opentelemetry/proto/trace/v1/trace.proto
+++ b/opentelemetry/proto/trace/v1/trace.proto
@@ -19,6 +19,7 @@ package opentelemetry.proto.trace.v1;
 import "opentelemetry/proto/common/v1/common.proto";
 import "opentelemetry/proto/resource/v1/resource.proto";
 
+option csharp_namespace = "OpenTelemetry.Proto.Trace.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.trace.v1";
 option java_outer_classname = "TraceProto";
diff --git a/opentelemetry/proto/trace/v1/trace_config.proto b/opentelemetry/proto/trace/v1/trace_config.proto
index 43f038a7f..aae19c9a2 100644
--- a/opentelemetry/proto/trace/v1/trace_config.proto
+++ b/opentelemetry/proto/trace/v1/trace_config.proto
@@ -16,6 +16,7 @@ syntax = "proto3";
 
 package opentelemetry.proto.trace.v1;
 
+option csharp_namespace = "OpenTelemetry.Proto.Collector.Trace.V1";
 option java_multiple_files = true;
 option java_package = "io.opentelemetry.proto.trace.v1";
 option java_outer_classname = "TraceConfigProto";