diff --git a/distribution/changelog.txt b/distribution/changelog.txt
index e73cc41948..ce36403b1d 100644
--- a/distribution/changelog.txt
+++ b/distribution/changelog.txt
@@ -1,7 +1,8 @@
 0.3.1+ (in development)
 ------------------------------------------------------------------------
-- Feature: [#13000] objective_options command for console
-- Fix: [#3200] Close Construction window upon selecting vehicle page
+- Feature: [#12999] .sea (RCT Classic) scenarios are now listed in the “New Scenario” dialog.
+- Feature: [#13000] objective_options command for console.
+- Fix: [#3200] Close Construction window upon selecting vehicle page.
 - Improved: [#13023] Made add_news_item console command last argument, assoc, optional.
 
 0.3.1 (2020-09-27)
diff --git a/distribution/linux/openrct2-mimeinfo.xml b/distribution/linux/openrct2-mimeinfo.xml
index 9f616ebb6e..7b72a6b3bb 100644
--- a/distribution/linux/openrct2-mimeinfo.xml
+++ b/distribution/linux/openrct2-mimeinfo.xml
@@ -49,6 +49,7 @@
     <comment xml:lang="zh-TW">OpenRCT2 劇情檔案</comment>
     <glob weight="60" pattern="*.sc6"/>
     <glob weight="60" pattern="*.sc4"/>
+    <glob weight="60" pattern="*.sea"/>
   </mime-type>
 
 </mime-info>
diff --git a/src/openrct2/FileClassifier.cpp b/src/openrct2/FileClassifier.cpp
index 77fedaf7d2..6f6fd74ee3 100644
--- a/src/openrct2/FileClassifier.cpp
+++ b/src/openrct2/FileClassifier.cpp
@@ -175,6 +175,8 @@ uint32_t get_file_extension_type(const utf8* path)
         return FILE_EXTENSION_TD4;
     if (String::Equals(extension, ".sc6", true))
         return FILE_EXTENSION_SC6;
+    if (String::Equals(extension, ".sea", true))
+        return FILE_EXTENSION_SC6;
     if (String::Equals(extension, ".sv6", true))
         return FILE_EXTENSION_SV6;
     if (String::Equals(extension, ".sv7", true))
diff --git a/src/openrct2/ParkImporter.cpp b/src/openrct2/ParkImporter.cpp
index c812df4bf1..a8483a582d 100644
--- a/src/openrct2/ParkImporter.cpp
+++ b/src/openrct2/ParkImporter.cpp
@@ -42,6 +42,7 @@ namespace ParkImporter
 
     bool ExtensionIsScenario(const std::string& extension)
     {
-        return String::Equals(extension, ".sc4", true) || String::Equals(extension, ".sc6", true);
+        return String::Equals(extension, ".sc4", true) || String::Equals(extension, ".sc6", true)
+            || String::Equals(extension, ".sea", true);
     }
 } // namespace ParkImporter
diff --git a/src/openrct2/platform/Platform.Win32.cpp b/src/openrct2/platform/Platform.Win32.cpp
index 99b77f5821..59110fa973 100644
--- a/src/openrct2/platform/Platform.Win32.cpp
+++ b/src/openrct2/platform/Platform.Win32.cpp
@@ -363,6 +363,7 @@ namespace Platform
         SetUpFileAssociation(".sv4", "RCT1 Saved Game (.sc4)", "Play", "\"%1\"", 0);
         SetUpFileAssociation(".sv6", "RCT2 Saved Game (.sv6)", "Play", "\"%1\"", 0);
         SetUpFileAssociation(".sv7", "RCT Modified Saved Game (.sv7)", "Play", "\"%1\"", 0);
+        SetUpFileAssociation(".sea", "RCTC Saved Game (.sea)", "Play", "\"%1\"", 0);
         SetUpFileAssociation(".td4", "RCT1 Track Design (.td4)", "Install", "\"%1\"", 0);
         SetUpFileAssociation(".td6", "RCT2 Track Design (.td6)", "Install", "\"%1\"", 0);
 
@@ -507,6 +508,7 @@ namespace Platform
         RemoveFileAssociation(".sv4");
         RemoveFileAssociation(".sv6");
         RemoveFileAssociation(".sv7");
+        RemoveFileAssociation(".sea");
         RemoveFileAssociation(".td4");
         RemoveFileAssociation(".td6");
 
diff --git a/src/openrct2/scenario/ScenarioRepository.cpp b/src/openrct2/scenario/ScenarioRepository.cpp
index 57790b0345..21f3432dc9 100644
--- a/src/openrct2/scenario/ScenarioRepository.cpp
+++ b/src/openrct2/scenario/ScenarioRepository.cpp
@@ -18,6 +18,7 @@
 #include "../core/File.h"
 #include "../core/FileIndex.hpp"
 #include "../core/FileStream.hpp"
+#include "../core/MemoryStream.h"
 #include "../core/Path.hpp"
 #include "../core/String.hpp"
 #include "../localisation/Language.h"
@@ -128,7 +129,7 @@ class ScenarioFileIndex final : public FileIndex<scenario_index_entry>
 private:
     static constexpr uint32_t MAGIC_NUMBER = 0x58444953; // SIDX
     static constexpr uint16_t VERSION = 3;
-    static constexpr auto PATTERN = "*.sc4;*.sc6";
+    static constexpr auto PATTERN = "*.sc4;*.sc6;*.sea";
 
 public:
     explicit ScenarioFileIndex(const IPlatformEnvironment& env)
@@ -203,6 +204,22 @@ protected:
     }
 
 private:
+    static std::unique_ptr<IStream> GetStreamFromRCT2Scenario(const std::string& path)
+    {
+        if (String::Equals(Path::GetExtension(path), ".sea", true))
+        {
+            auto data = DecryptSea(fs::u8path(path));
+            auto ms = std::make_unique<MemoryStream>();
+            // Need to copy the data into MemoryStream as the overload will borrow instead of copy.
+            ms->Write(data.data(), data.size());
+            ms->SetPosition(0);
+            return ms;
+        }
+
+        auto fs = std::make_unique<FileStream>(path, FILE_MODE_OPEN);
+        return fs;
+    }
+
     /**
      * Reads basic information from a scenario file.
      */
@@ -234,9 +251,9 @@ private:
             }
             else
             {
-                // RCT2 scenario
-                auto fs = FileStream(path, FILE_MODE_OPEN);
-                auto chunkReader = SawyerChunkReader(&fs);
+                // RCT2 or RCTC scenario
+                auto stream = GetStreamFromRCT2Scenario(path);
+                auto chunkReader = SawyerChunkReader(stream.get());
 
                 rct_s6_header header = chunkReader.ReadChunkAs<rct_s6_header>();
                 if (header.type == S6_TYPE_SCENARIO)