diff --git a/dotnet/src/dotnetcore/Providers/Storage/GXAmazonS3/GXAmazonS3.csproj b/dotnet/src/dotnetcore/Providers/Storage/GXAmazonS3/GXAmazonS3.csproj
index 927009f41..b11dd9a68 100644
--- a/dotnet/src/dotnetcore/Providers/Storage/GXAmazonS3/GXAmazonS3.csproj
+++ b/dotnet/src/dotnetcore/Providers/Storage/GXAmazonS3/GXAmazonS3.csproj
@@ -9,6 +9,7 @@
 	</PropertyGroup>
   <ItemGroup>
     <Compile Include="..\..\..\..\dotnetframework\Providers\Storage\GXAmazonS3\ExternalProviderS3.cs" Link="ExternalProviderS3.cs" />
+	<Compile Include="..\..\..\..\dotnetframework\Providers\Storage\GXAmazonS3\S3UploadStream.cs" Link="S3UploadStream.cs" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/dotnet/src/dotnetframework/Providers/Storage/GXAmazonS3/ExternalProviderS3.cs b/dotnet/src/dotnetframework/Providers/Storage/GXAmazonS3/ExternalProviderS3.cs
index 91faea310..bacfba907 100644
--- a/dotnet/src/dotnetframework/Providers/Storage/GXAmazonS3/ExternalProviderS3.cs
+++ b/dotnet/src/dotnetframework/Providers/Storage/GXAmazonS3/ExternalProviderS3.cs
@@ -2,10 +2,8 @@
 using Amazon.S3;
 using Amazon.S3.IO;
 using Amazon.S3.Model;
-using GeneXus.Encryption;
 using GeneXus.Services;
 using GeneXus.Utils;
-using log4net;
 using System;
 using System.Collections.Generic;
 using System.IO;
@@ -362,18 +360,44 @@ private S3CannedACL GetCannedACL(GxFileType acl)
 			}
 		}
 
+		const long MIN_MULTIPART_POST = 10L * 1024 * 1024;
+
 		public string Upload(string fileName, Stream stream, GxFileType destFileType)
 		{
-			MemoryStream ms = new MemoryStream();
-			stream.CopyTo(ms);//can determine PutObjectRequest.Headers.ContentLength. Avoid error Could not determine content length
+			bool doSimpleUpload = stream.CanSeek && stream.Length <= MIN_MULTIPART_POST;
+			if (doSimpleUpload)
+			{
+				return UploadSimple(fileName, stream, destFileType);
+			}
+			else
+			{
+				return UploadMultipart(fileName, stream, destFileType);
+			}			
+		}
+
+		private string UploadMultipart(string fileName, Stream stream, GxFileType destFileType)
+		{
+			string contentType = null;
+			TryGetContentType(fileName, out contentType);
+			
+			using (S3UploadStream s = new S3UploadStream(Client, Bucket, fileName, GetCannedACL(destFileType), contentType))
+			{
+				stream.CopyTo(s);
+			}
+			return Get(fileName, destFileType);
+		}
+
+		private string UploadSimple(string fileName, Stream stream, GxFileType destFileType)
+		{			
 			PutObjectRequest objectRequest = new PutObjectRequest()
 			{
 				BucketName = Bucket,
 				Key = fileName,
-				InputStream = ms,
+				InputStream = stream,
 				CannedACL = GetCannedACL(destFileType)
 			};
-			if (TryGetContentType(fileName, out string mimeType)) {
+			if (TryGetContentType(fileName, out string mimeType))
+			{
 				objectRequest.ContentType = mimeType;
 			}
 			PutObjectResponse result = PutObject(objectRequest);
diff --git a/dotnet/src/dotnetframework/Providers/Storage/GXAmazonS3/S3UploadStream.cs b/dotnet/src/dotnetframework/Providers/Storage/GXAmazonS3/S3UploadStream.cs
new file mode 100644
index 000000000..c3d195403
--- /dev/null
+++ b/dotnet/src/dotnetframework/Providers/Storage/GXAmazonS3/S3UploadStream.cs
@@ -0,0 +1,210 @@
+using Amazon.S3;
+using Amazon.S3.Model;
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace GeneXus.Storage.GXAmazonS3
+{
+	public class S3UploadStream : Stream
+	{
+		/* Note the that maximum size (as of now) of a file in S3 is 5TB so it isn't
+         * safe to assume all uploads will work here.  MAX_PART_SIZE times MAX_PART_COUNT
+         * is ~50TB, which is too big for S3. */
+		const long MIN_PART_LENGTH = 5L * 1024 * 1024; // all parts but the last this size or greater
+		const long MAX_PART_LENGTH = 5L * 1024 * 1024 * 1024; // 5GB max per PUT
+		const long MAX_PART_COUNT = 10000; // no more than 10,000 parts total
+		const long DEFAULT_PART_LENGTH = MIN_PART_LENGTH;
+
+		internal class Metadata
+		{
+			public string BucketName { get; set; }
+			public string Key { get; set; }
+			public long PartLength { get; set; } = DEFAULT_PART_LENGTH;
+
+			public int PartCount { get; set; } = 0;
+			public string UploadId { get; set; }
+			public MemoryStream CurrentStream { get; set; }
+			public S3CannedACL Acl { get; set; }
+			public string ContentType { get; set; }
+
+			public long Position { get; set; } = 0;
+			public long Length { get; set; } = 0;
+
+			public List<Task> Tasks = new List<Task>();
+			public ConcurrentDictionary<int, string> PartETags = new ConcurrentDictionary<int, string>();
+		}
+
+		Metadata _metadata = new Metadata();
+		IAmazonS3 _s3 = null;
+
+		public S3UploadStream(IAmazonS3 s3, string s3uri, long partLength = DEFAULT_PART_LENGTH)
+			: this(s3, new Uri(s3uri), partLength)
+		{
+		}
+
+		public S3UploadStream(IAmazonS3 s3, Uri s3uri, long partLength = DEFAULT_PART_LENGTH)
+			: this(s3, s3uri.Host, s3uri.LocalPath.Substring(1), partLength)
+		{
+		}
+		public S3UploadStream(IAmazonS3 s3, string bucket, string key, long partLength = DEFAULT_PART_LENGTH)
+			: this(s3, bucket, key, null, null, partLength)
+		{
+
+		}
+		public S3UploadStream(IAmazonS3 s3, string bucket, string key, S3CannedACL acl, string cType = null, long partLength = DEFAULT_PART_LENGTH)
+		{
+			_s3 = s3;
+			_metadata.BucketName = bucket;
+			_metadata.Key = key;
+			_metadata.PartLength = partLength;
+			_metadata.Acl = acl;
+			_metadata.ContentType = cType;
+		}
+
+		protected override void Dispose(bool disposing)
+		{
+			if (disposing)
+			{
+				if (_metadata != null)
+				{
+					Flush(true);
+					CompleteUpload();
+				}
+			}
+			_metadata = null;
+			base.Dispose(disposing);
+		}
+
+		public override bool CanRead => false;
+		public override bool CanSeek => false;
+		public override bool CanWrite => true;
+		public override long Length => _metadata.Length = Math.Max(_metadata.Length, _metadata.Position);
+
+		public override long Position
+		{
+			get => _metadata.Position;
+			set => throw new NotImplementedException();
+		}
+
+		public override int Read(byte[] buffer, int offset, int count) => throw new NotImplementedException();
+		public override long Seek(long offset, SeekOrigin origin) => throw new NotImplementedException();
+
+		public override void SetLength(long value)
+		{
+			_metadata.Length = Math.Max(_metadata.Length, value);
+			_metadata.PartLength = Math.Max(MIN_PART_LENGTH, Math.Min(MAX_PART_LENGTH, _metadata.Length / MAX_PART_COUNT));
+		}
+
+		private void StartNewPart()
+		{
+			if (_metadata.CurrentStream != null)
+			{
+				Flush(false);
+			}
+			_metadata.CurrentStream = new MemoryStream();
+			_metadata.PartLength = Math.Min(MAX_PART_LENGTH, Math.Max(_metadata.PartLength, (_metadata.PartCount / 2 + 1) * MIN_PART_LENGTH));
+		}
+
+		public override void Flush()
+		{
+			Flush(false);
+		}
+
+		private void Flush(bool disposing)
+		{
+			if ((_metadata.CurrentStream == null || _metadata.CurrentStream.Length < MIN_PART_LENGTH) &&
+				!disposing)
+				return;
+
+			if (_metadata.UploadId == null)
+			{
+
+				InitiateMultipartUploadRequest uploadRequest = new InitiateMultipartUploadRequest()
+				{
+					BucketName = _metadata.BucketName,
+					Key = _metadata.Key					
+				};
+
+				if (_metadata.Acl != null)
+				{
+					uploadRequest.CannedACL = _metadata.Acl;
+				}
+
+				if (!string.IsNullOrEmpty(_metadata.ContentType))
+				{
+					uploadRequest.ContentType = _metadata.ContentType;
+				}
+				_metadata.UploadId = _s3.InitiateMultipartUploadAsync(uploadRequest).GetAwaiter().GetResult().UploadId;
+			}
+
+			if (_metadata.CurrentStream != null)
+			{
+				int i = ++_metadata.PartCount;
+
+				_metadata.CurrentStream.Seek(0, SeekOrigin.Begin);
+				var request = new UploadPartRequest()
+				{
+					BucketName = _metadata.BucketName,
+					Key = _metadata.Key,
+					UploadId = _metadata.UploadId,
+					PartNumber = i,
+					IsLastPart = disposing,
+					InputStream = _metadata.CurrentStream
+				};
+				_metadata.CurrentStream = null;
+
+				var upload = Task.Run(() =>
+				{
+					UploadPartResponse response = _s3.UploadPartAsync(request).GetAwaiter().GetResult();
+					_metadata.PartETags.AddOrUpdate(i, response.ETag,
+						(n, s) => response.ETag);
+					request.InputStream.Dispose();
+				});
+				_metadata.Tasks.Add(upload);
+			}
+		}
+
+		private void CompleteUpload()
+		{
+			Task.WaitAll(_metadata.Tasks.ToArray());
+
+			if (Length > 0)
+			{
+				_s3.CompleteMultipartUploadAsync(new CompleteMultipartUploadRequest()
+				{
+					BucketName = _metadata.BucketName,
+					Key = _metadata.Key,
+					PartETags = _metadata.PartETags.Select(e => new PartETag(e.Key, e.Value)).ToList(),
+					UploadId = _metadata.UploadId
+				}).GetAwaiter().GetResult();
+			}
+		}
+
+		public override void Write(byte[] buffer, int offset, int count)
+		{
+			if (count == 0) return;
+
+			// write as much of the buffer as will fit to the current part, and if needed
+			// allocate a new part and continue writing to it (and so on).
+			int o = offset;
+			int c = Math.Min(count, buffer.Length - offset); // don't over-read the buffer, even if asked to
+			do
+			{
+				if (_metadata.CurrentStream == null || _metadata.CurrentStream.Length >= _metadata.PartLength)
+					StartNewPart();
+
+				long remaining = _metadata.PartLength - _metadata.CurrentStream.Length;
+				int w = Math.Min(c, (int)remaining);
+				_metadata.CurrentStream.Write(buffer, o, w);
+
+				_metadata.Position += w;
+				c -= w;
+				o += w;
+			} while (c > 0);
+		}
+	}
+}
\ No newline at end of file