diff --git a/cmd/envbuilder/main.go b/cmd/envbuilder/main.go
index e8dc220..91cde8a 100644
--- a/cmd/envbuilder/main.go
+++ b/cmd/envbuilder/main.go
@@ -75,6 +75,10 @@ func envbuilderCmd() serpent.Command {
 				}
 			}
 
+			if o.GitSSHPrivateKeyPath != "" && o.GitSSHPrivateKeyBase64 != "" {
+				return errors.New("cannot have both GIT_SSH_PRIVATE_KEY_PATH and GIT_SSH_PRIVATE_KEY_BASE64 set")
+			}
+
 			if o.GetCachedImage {
 				img, err := envbuilder.RunCacheProbe(inv.Context(), o)
 				if err != nil {
diff --git a/docs/env-variables.md b/docs/env-variables.md
index 1c80f4f..5513fd5 100644
--- a/docs/env-variables.md
+++ b/docs/env-variables.md
@@ -27,7 +27,8 @@
 | `--git-clone-single-branch` | `ENVBUILDER_GIT_CLONE_SINGLE_BRANCH` |  | Clone only a single branch of the Git repository. |
 | `--git-username` | `ENVBUILDER_GIT_USERNAME` |  | The username to use for Git authentication. This is optional. |
 | `--git-password` | `ENVBUILDER_GIT_PASSWORD` |  | The password to use for Git authentication. This is optional. |
-| `--git-ssh-private-key-path` | `ENVBUILDER_GIT_SSH_PRIVATE_KEY_PATH` |  | Path to an SSH private key to be used for Git authentication. |
+| `--git-ssh-private-key-path` | `ENVBUILDER_GIT_SSH_PRIVATE_KEY_PATH` |  | Path to an SSH private key to be used for Git authentication. If this is set, then GIT_SSH_PRIVATE_KEY_BASE64 cannot be set. |
+| `--git-ssh-private-key-base64` | `ENVBUILDER_GIT_SSH_PRIVATE_KEY_BASE64` |  | Base64 encoded SSH private key to be used for Git authentication. If this is set, then GIT_SSH_PRIVATE_KEY_PATH cannot be set. |
 | `--git-http-proxy-url` | `ENVBUILDER_GIT_HTTP_PROXY_URL` |  | The URL for the HTTP proxy. This is optional. |
 | `--workspace-folder` | `ENVBUILDER_WORKSPACE_FOLDER` |  | The path to the workspace folder that will be built. This is optional. |
 | `--ssl-cert-base64` | `ENVBUILDER_SSL_CERT_BASE64` |  | The content of an SSL cert file. This is useful for self-signed certificates. |
diff --git a/git/git.go b/git/git.go
index 7d132c3..f37b968 100644
--- a/git/git.go
+++ b/git/git.go
@@ -2,6 +2,7 @@ package git
 
 import (
 	"context"
+	"encoding/base64"
 	"errors"
 	"fmt"
 	"io"
@@ -181,6 +182,22 @@ func ReadPrivateKey(path string) (gossh.Signer, error) {
 	return k, nil
 }
 
+// DecodeBase64PrivateKey attempts to decode a base64 encoded private
+// key and returns an ssh.Signer
+func DecodeBase64PrivateKey(key string) (gossh.Signer, error) {
+	bs, err := base64.StdEncoding.DecodeString(key)
+	if err != nil {
+		return nil, fmt.Errorf("decode base64: %w", err)
+	}
+
+	k, err := gossh.ParsePrivateKey(bs)
+	if err != nil {
+		return nil, fmt.Errorf("parse private key: %w", err)
+	}
+
+	return k, nil
+}
+
 // LogHostKeyCallback is a HostKeyCallback that just logs host keys
 // and does nothing else.
 func LogHostKeyCallback(logger func(string, ...any)) gossh.HostKeyCallback {
@@ -273,6 +290,17 @@ func SetupRepoAuth(logf func(string, ...any), options *options.Options) transpor
 		}
 	}
 
+	// If no path was provided, fall back to the environment variable
+	if options.GitSSHPrivateKeyBase64 != "" {
+		s, err := DecodeBase64PrivateKey(options.GitSSHPrivateKeyBase64)
+		if err != nil {
+			logf("❌ Failed to decode base 64 private key: %s", err.Error())
+		} else {
+			logf("🔑 Using %s key!", s.PublicKey().Type())
+			signer = s
+		}
+	}
+
 	// If no SSH key set, fall back to agent auth.
 	if signer == nil {
 		logf("🔑 No SSH key found, falling back to agent!")
diff --git a/git/git_test.go b/git/git_test.go
index e7a58f9..0da5a16 100644
--- a/git/git_test.go
+++ b/git/git_test.go
@@ -3,6 +3,7 @@ package git_test
 import (
 	"context"
 	"crypto/ed25519"
+	"encoding/base64"
 	"fmt"
 	"io"
 	"net/http/httptest"
@@ -433,6 +434,22 @@ func TestSetupRepoAuth(t *testing.T) {
 		require.Equal(t, actualSigner, pk.Signer)
 	})
 
+	t.Run("SSH/Base64PrivateKey", func(t *testing.T) {
+		opts := &options.Options{
+			GitURL:                 "ssh://git@host.tld:repo/path",
+			GitSSHPrivateKeyBase64: base64EncodeTestPrivateKey(),
+		}
+		auth := git.SetupRepoAuth(t.Logf, opts)
+
+		pk, ok := auth.(*gitssh.PublicKeys)
+		require.True(t, ok)
+		require.NotNil(t, pk.Signer)
+
+		actualSigner, err := gossh.ParsePrivateKey([]byte(testKey))
+		require.NoError(t, err)
+		require.Equal(t, actualSigner, pk.Signer)
+	})
+
 	t.Run("SSH/NoAuthMethods", func(t *testing.T) {
 		opts := &options.Options{
 			GitURL: "ssh://git@host.tld:repo/path",
@@ -502,3 +519,7 @@ func writeTestPrivateKey(t *testing.T) string {
 	require.NoError(t, os.WriteFile(kPath, []byte(testKey), 0o600))
 	return kPath
 }
+
+func base64EncodeTestPrivateKey() string {
+	return base64.StdEncoding.EncodeToString([]byte(testKey))
+}
diff --git a/integration/integration_test.go b/integration/integration_test.go
index deb21ef..9413c34 100644
--- a/integration/integration_test.go
+++ b/integration/integration_test.go
@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"crypto/ed25519"
 	"encoding/base64"
 	"encoding/json"
 	"encoding/pem"
@@ -32,6 +33,8 @@ import (
 	"github.com/coder/envbuilder/testutil/gittest"
 	"github.com/coder/envbuilder/testutil/mwtest"
 	"github.com/coder/envbuilder/testutil/registrytest"
+	"github.com/go-git/go-billy/v5/osfs"
+	gossh "golang.org/x/crypto/ssh"
 
 	clitypes "github.com/docker/cli/cli/config/types"
 	"github.com/docker/docker/api/types"
@@ -58,6 +61,16 @@ const (
 	testContainerLabel = "envbox-integration-test"
 	testImageAlpine    = "localhost:5000/envbuilder-test-alpine:latest"
 	testImageUbuntu    = "localhost:5000/envbuilder-test-ubuntu:latest"
+
+	// nolint:gosec // Throw-away key for testing. DO NOT REUSE.
+	testSSHKey = `-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
+QyNTUxOQAAACBXOGgAge/EbcejqASqZa6s8PFXZle56DiGEt0VYnljuwAAAKgM05mUDNOZ
+lAAAAAtzc2gtZWQyNTUxOQAAACBXOGgAge/EbcejqASqZa6s8PFXZle56DiGEt0VYnljuw
+AAAEDCawwtjrM4AGYXD1G6uallnbsgMed4cfkFsQ+mLZtOkFc4aACB78Rtx6OoBKplrqzw
+8VdmV7noOIYS3RVieWO7AAAAHmNpYW5AY2RyLW1icC1mdmZmdzBuOHEwNXAuaG9tZQECAw
+QFBgc=
+-----END OPENSSH PRIVATE KEY-----`
 )
 
 func TestLogs(t *testing.T) {
@@ -378,6 +391,54 @@ func TestSucceedsGitAuth(t *testing.T) {
 	require.Contains(t, gitConfig, srv.URL)
 }
 
+func TestGitSSHAuth(t *testing.T) {
+	t.Parallel()
+
+	base64Key := base64.StdEncoding.EncodeToString([]byte(testSSHKey))
+
+	t.Run("Base64/Success", func(t *testing.T) {
+		signer, err := gossh.ParsePrivateKey([]byte(testSSHKey))
+		require.NoError(t, err)
+		require.NotNil(t, signer)
+
+		tmpDir := t.TempDir()
+		srvFS := osfs.New(tmpDir, osfs.WithChrootOS())
+
+		_ = gittest.NewRepo(t, srvFS, gittest.Commit(t, "Dockerfile", "FROM "+testImageAlpine, "Initial commit"))
+		tr := gittest.NewServerSSH(t, srvFS, signer.PublicKey())
+
+		_, err = runEnvbuilder(t, runOpts{env: []string{
+			envbuilderEnv("DOCKERFILE_PATH", "Dockerfile"),
+			envbuilderEnv("GIT_URL", tr.String()+"."),
+			envbuilderEnv("GIT_SSH_PRIVATE_KEY_BASE64", base64Key),
+		}})
+		// TODO: Ensure it actually clones but this does mean we have
+		// successfully authenticated.
+		require.ErrorContains(t, err, "repository not found")
+	})
+
+	t.Run("Base64/Failure", func(t *testing.T) {
+		_, randomKey, err := ed25519.GenerateKey(nil)
+		require.NoError(t, err)
+		signer, err := gossh.NewSignerFromKey(randomKey)
+		require.NoError(t, err)
+		require.NotNil(t, signer)
+
+		tmpDir := t.TempDir()
+		srvFS := osfs.New(tmpDir, osfs.WithChrootOS())
+
+		_ = gittest.NewRepo(t, srvFS, gittest.Commit(t, "Dockerfile", "FROM "+testImageAlpine, "Initial commit"))
+		tr := gittest.NewServerSSH(t, srvFS, signer.PublicKey())
+
+		_, err = runEnvbuilder(t, runOpts{env: []string{
+			envbuilderEnv("DOCKERFILE_PATH", "Dockerfile"),
+			envbuilderEnv("GIT_URL", tr.String()+"."),
+			envbuilderEnv("GIT_SSH_PRIVATE_KEY_BASE64", base64Key),
+		}})
+		require.ErrorContains(t, err, "handshake failed")
+	})
+}
+
 func TestSucceedsGitAuthInURL(t *testing.T) {
 	t.Parallel()
 	srv := gittest.CreateGitServer(t, gittest.Options{
diff --git a/options/options.go b/options/options.go
index 18bd56d..ed6bfa9 100644
--- a/options/options.go
+++ b/options/options.go
@@ -108,6 +108,9 @@ type Options struct {
 	// GitSSHPrivateKeyPath is the path to an SSH private key to be used for
 	// Git authentication.
 	GitSSHPrivateKeyPath string
+	// GitSSHPrivateKeyBase64 is the content of an SSH private key to be used
+	// for Git authentication.
+	GitSSHPrivateKeyBase64 string
 	// GitHTTPProxyURL is the URL for the HTTP proxy. This is optional.
 	GitHTTPProxyURL string
 	// WorkspaceFolder is the path to the workspace folder that will be built.
@@ -358,10 +361,18 @@ func (o *Options) CLI() serpent.OptionSet {
 			Description: "The password to use for Git authentication. This is optional.",
 		},
 		{
-			Flag:        "git-ssh-private-key-path",
-			Env:         WithEnvPrefix("GIT_SSH_PRIVATE_KEY_PATH"),
-			Value:       serpent.StringOf(&o.GitSSHPrivateKeyPath),
-			Description: "Path to an SSH private key to be used for Git authentication.",
+			Flag:  "git-ssh-private-key-path",
+			Env:   WithEnvPrefix("GIT_SSH_PRIVATE_KEY_PATH"),
+			Value: serpent.StringOf(&o.GitSSHPrivateKeyPath),
+			Description: "Path to an SSH private key to be used for Git authentication." +
+				" If this is set, then GIT_SSH_PRIVATE_KEY_BASE64 cannot be set.",
+		},
+		{
+			Flag:  "git-ssh-private-key-base64",
+			Env:   WithEnvPrefix("GIT_SSH_PRIVATE_KEY_BASE64"),
+			Value: serpent.StringOf(&o.GitSSHPrivateKeyBase64),
+			Description: "Base64 encoded SSH private key to be used for Git authentication." +
+				" If this is set, then GIT_SSH_PRIVATE_KEY_PATH cannot be set.",
 		},
 		{
 			Flag:        "git-http-proxy-url",
diff --git a/options/testdata/options.golden b/options/testdata/options.golden
index 0bfbd64..518f774 100644
--- a/options/testdata/options.golden
+++ b/options/testdata/options.golden
@@ -94,8 +94,13 @@ OPTIONS:
       --git-password string, $ENVBUILDER_GIT_PASSWORD
           The password to use for Git authentication. This is optional.
 
+      --git-ssh-private-key-base64 string, $ENVBUILDER_GIT_SSH_PRIVATE_KEY_BASE64
+          Base64 encoded SSH private key to be used for Git authentication. If
+          this is set, then GIT_SSH_PRIVATE_KEY_PATH cannot be set.
+
       --git-ssh-private-key-path string, $ENVBUILDER_GIT_SSH_PRIVATE_KEY_PATH
-          Path to an SSH private key to be used for Git authentication.
+          Path to an SSH private key to be used for Git authentication. If this
+          is set, then GIT_SSH_PRIVATE_KEY_BASE64 cannot be set.
 
       --git-url string, $ENVBUILDER_GIT_URL
           The URL of a Git repository containing a Devcontainer or Docker image