diff --git a/TODO.txt b/TODO.txt
index d71c644..95377ba 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -11,11 +11,13 @@ Key:
 Milestone: v0.3.0
 -----------------
 
-[ ] Stream API
+[~] Stream API
+    [~] Implementation
+    [ ] Convert all HTTP code and JSON code
+    [ ] Multi-output (proof of concept)
     [ ] TLS
     [ ] SOCKS
-    [ ] Multi-output
-    [ ] Move UtilStreamCopy()
+    [ ] Move/convert UtilStreamCopy()
 [~] HTTP Client API
     [x] Document HttpParseHeaders()
     [ ] HttpClient man page
diff --git a/src/Stream.c b/src/Stream.c
new file mode 100644
index 0000000..d6afbb8
--- /dev/null
+++ b/src/Stream.c
@@ -0,0 +1,170 @@
+#include <Stream.h>
+
+#include <Memory.h>
+
+#include <errno.h>
+
+struct Stream
+{
+    StreamFunctions io;
+    void *cookie;
+
+    int *ub;
+    size_t ubSize;
+    size_t ubLen;
+};
+
+Stream *
+StreamCreate(void *cookie, StreamFunctions funcs)
+{
+    Stream *stream;
+
+    if (!funcs.read || !funcs.write)
+    {
+        return NULL;
+    }
+
+    stream = Malloc(sizeof(Stream));
+
+    if (!stream)
+    {
+        return NULL;
+    }
+
+    stream->cookie = cookie;
+
+    stream->io.read = funcs.read;
+    stream->io.write = funcs.write;
+    stream->io.seek = funcs.seek;
+    stream->io.close = funcs.close;
+
+    stream->ubSize = 0;
+
+    return stream;
+}
+
+ssize_t
+StreamRead(Stream *stream, void *buf, size_t nBytes)
+{
+    if (!stream)
+    {
+        errno = EBADF;
+        return -1;
+    }
+
+    return stream->io.read(stream->cookie, buf, nBytes);
+}
+
+ssize_t
+StreamWrite(Stream *stream, void *buf, size_t nBytes)
+{
+    if (!stream)
+    {
+        errno = EBADF;
+        return -1;
+    }
+
+    return stream->io.write(stream->cookie, buf, nBytes);
+}
+
+off_t
+StreamSeek(Stream *stream, off_t offset, int whence)
+{
+    if (!stream)
+    {
+        errno = EBADF;
+        return -1;
+    }
+
+    if (!stream->io.seek)
+    {
+        errno = EINVAL;
+        return -1;
+    }
+
+    return stream->io.seek(stream->cookie, offset, whence);
+}
+
+int
+StreamClose(Stream *stream)
+{
+    int ret;
+
+    if (!stream)
+    {
+        errno = EBADF;
+        return -1;
+    }
+
+    if (stream->io.close)
+    {
+        ret = stream->io.close(stream->cookie);
+    }
+    else
+    {
+        ret = 0;
+    }
+
+    if (stream->ubSize)
+    {
+        Free(stream->ub);
+    }
+
+    Free(stream);
+
+    return ret;
+}
+
+static ssize_t
+StreamReadFd(void *cookie, void *buf, size_t nBytes)
+{
+    int fd = *((int *) cookie);
+
+    return read(fd, buf, nBytes);
+}
+
+static ssize_t
+StreamWriteFd(void *cookie, void *buf, size_t nBytes)
+{
+    int fd = *((int *) cookie);
+
+    return write(fd, buf, nBytes);
+}
+
+static off_t
+StreamSeekFd(void *cookie, off_t offset, int whence)
+{
+    int fd = *((int *) cookie);
+
+    return lseek(fd, offset, whence);
+}
+
+static int
+StreamCloseFd(void *cookie)
+{
+    int fd = *((int *) cookie);
+
+    return close(fd);
+}
+
+Stream *
+StreamOpen(int fd)
+{
+    int *fdp = Malloc(sizeof(int));
+    StreamFunctions f;
+
+    if (!fdp)
+    {
+        return NULL;
+    }
+
+    *fdp = fd;
+
+    f.read = StreamReadFd;
+    f.write = StreamWriteFd;
+    f.seek = StreamSeekFd;
+    f.close = StreamCloseFd;
+
+    return StreamCreate(fdp, f);
+
+}
diff --git a/src/include/Stream.h b/src/include/Stream.h
new file mode 100644
index 0000000..3a14ab8
--- /dev/null
+++ b/src/include/Stream.h
@@ -0,0 +1,73 @@
+#ifndef TELODENDRIA_STREAM_H
+#define TELODENDRIA_STREAM_H
+
+#include <unistd.h>
+#include <stdarg.h>
+
+typedef struct Stream Stream;
+
+/*
+ * Low-level Stream API in the style of POSIX system calls.
+ * Heavily inspired by GNU fopencookie() and BSD funopen().
+ */
+
+typedef ssize_t (StreamReadFunc) (void *, void *, size_t);
+typedef ssize_t (StreamWriteFunc) (void *, void *, size_t);
+typedef off_t (StreamSeekFunc) (void *, off_t, int);
+typedef int (StreamCloseFunc) (void *);
+
+typedef struct StreamFunctions
+{
+    StreamReadFunc *read;
+    StreamWriteFunc *write;
+    StreamSeekFunc *seek;
+    StreamCloseFunc *close;
+} StreamFunctions;
+
+extern Stream *
+StreamCreate(void *, StreamFunctions);
+
+extern ssize_t
+StreamRead(Stream *, void *, size_t);
+
+extern ssize_t
+StreamWrite(Stream *, void *, size_t);
+
+extern off_t
+StreamSeek(Stream *, off_t, int);
+
+extern int
+StreamClose(Stream *);
+
+extern Stream *
+StreamOpen(int);
+
+/*
+ * High level Stream API in the style of C standard I/O.
+ */
+
+extern int
+StreamVprintf(Stream *, const char *, va_list);
+
+extern int
+StreamPrintf(Stream *, const char *, ...);
+
+extern int
+StreamGetc(Stream *);
+
+extern int
+StreamUngetc(Stream *, int);
+
+extern int
+StreamEof(Stream *);
+
+extern int
+StreamError(Stream *);
+
+extern void
+StreamClearError(Stream *);
+
+extern int
+StreamFlush(Stream *);
+
+#endif /* TELODENDRIA_STREAM_H */