diff --git a/NEWS.md b/NEWS.md
index deb37af8..91b96ce7 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # rsconnect 0.8.30 (development version)
 
+* `deployApp("foo.Rmd")` has been deprecated. It was never documented, and
+  it does the same job as `deployDoc()` (#698).
+
 * `deployApp(appPrimaryDoc)` has been deprecated; it did the same job as 
   `recordDir`.
 
diff --git a/R/deployApp.R b/R/deployApp.R
index 02bf9e0a..5d5af030 100644
--- a/R/deployApp.R
+++ b/R/deployApp.R
@@ -18,8 +18,8 @@
 #' control to ensure that future you and other collaborators will publish
 #' to the same location.
 #'
-#' @param appDir Directory containing application. Defaults to current working
-#'   directory.
+#' @param appDir A directory containing an application (e.g. a Shiny app
+#'   or plumber API). Defaults to the current directory.
 #' @param appFiles A character vector given relative paths to the files and
 #'   directories to bundle and deploy. The default, `NULL`, will include all
 #'   files in `appDir`, apart from any listed in an `.rscignore` file.
@@ -152,7 +152,29 @@ deployApp <- function(appDir = getwd(),
 
   condaMode <- FALSE
 
+  check_string(appDir)
+  if (isStaticFile(appDir) && !dirExists(appDir)) {
+    lifecycle::deprecate_warn(
+      when = "0.9.0",
+      what = "deployApp(appDir = 'takes a directory, not a document,')",
+      with = "deployDoc()"
+    )
+    return(deployDoc(
+      appDir,
+      appName = appName,
+      appTitle = appTitle,
+      account = account,
+      server = server,
+      upload = upload,
+      recordDir = recordDir,
+      launch.browser = launch.browser,
+      logLevel = logLevel,
+      lint = lint
+    ))
+  }
   check_directory(appDir)
+  appDir <- normalizePath(appDir)
+
   check_string(appName, allow_null = TRUE)
 
   if (!is.null(appPrimaryDoc)) {
@@ -207,26 +229,6 @@ deployApp <- function(appDir = getwd(),
     on.exit(options(old_error), add = TRUE)
   }
 
-  # normalize appDir path
-  appDir <- normalizePath(appDir)
-
-  # if a specific file is named, make sure it's an Rmd or HTML, and just deploy
-  # a single document in this case (this will call back to deployApp with a list
-  # of supporting documents)
-  rmdFile <- ""
-  if (!dirExists(appDir)) {
-    if (grepl("\\.[Rq]md$", appDir, ignore.case = TRUE) ||
-        grepl("\\.html?$", appDir, ignore.case = TRUE)) {
-      return(deployDoc(appDir, appName = appName, appTitle = appTitle,
-                       account = account, server = server, upload = upload,
-                       recordDir = recordDir, launch.browser = launch.browser,
-                       logLevel = logLevel, lint = lint))
-    } else {
-      stop(appDir, " must be a directory, an R Markdown document, or an HTML ",
-           "document.")
-    }
-  }
-
   # at verbose log level, generate header
   if (verbose) {
     logger("Deployment log started")
diff --git a/R/deployDoc.R b/R/deployDoc.R
index 4ac13df5..feea39f4 100644
--- a/R/deployDoc.R
+++ b/R/deployDoc.R
@@ -23,39 +23,51 @@
 #' @family Deployment functions
 #' @export
 deployDoc <- function(doc, ...) {
+  doc <- standardizeSingleDocDeployment(doc)
+  deployApp(
+    appDir = doc$appDir,
+    appPrimaryDoc = doc$appPrimaryDoc,
+    appFiles = doc$appFiles,
+    ...
+  )
+}
+
+standardizeSingleDocDeployment <- function(path,
+                                           quiet = FALSE,
+                                           error_call = caller_env(),
+                                           error_arg = caller_arg(path)) {
   check_installed(
     "rmarkdown",
     version = "0.5.2",
     reason = "to deploy individual R Markdown documents"
   )
+  check_file(path, error_call = error_call, error_arg = error_arg)
+  path <- normalizePath(path)
 
-  check_file(doc)
-
-  # get qualified doc
-  qualified_doc <- normalizePath(doc, winslash = "/")
+  withStatus <- withStatus(quiet)
 
-  # see if this doc has runtime: shiny_prerendered, if it does then
-  # appFiles will be NULL (bundle the entire directory)
-  if (isShinyRmd(doc)) {
-    app_files <- NULL
+  if (isShinyRmd(path)) {
+    # deploy entire directory
+    appFiles <- NULL
+  } else if (isStaticFile(path)) {
+    # deploy file + dependenciy
+    withStatus("Discovering document dependencies", {
+      resources <- rmarkdown::find_external_resources(path)
+    })
+    appFiles <- c(basename(path), resources$path)
   } else {
-    # default to deploying just the single file specified
-    app_files <- basename(qualified_doc)
-
-    # if this document's type supports automated resource discovery, do that now,
-    # and add the discovered files to the deployment list
-    ext <- tolower(tools::file_ext(doc))
-    if (ext %in% c("rmd", "qmd", "html", "htm")) {
-      message("Discovering document dependencies... ", appendLF = FALSE)
-      res <- rmarkdown::find_external_resources(qualified_doc)
-      message("OK")
-      app_files <- c(app_files, res$path)
-    }
+    # deploy just the file
+    appFiles <- basename(path)
   }
 
-  # deploy the document with the discovered dependencies
-  deployApp(appDir = dirname(qualified_doc),
-            appFiles = app_files,
-            appPrimaryDoc = basename(qualified_doc),
-            ...)
+  list(
+    appDir = normalizePath(dirname(path)),
+    appPrimaryDoc = basename(path),
+    appFiles = appFiles
+  )
+}
+
+isStaticFile <- function(path) {
+  ext <- tolower(tools::file_ext(path))
+  ext %in% c("rmd", "qmd", "html", "htm")
 }
diff --git a/man/deployApp.Rd b/man/deployApp.Rd
index 47b7f699..9218e5a0 100644
--- a/man/deployApp.Rd
+++ b/man/deployApp.Rd
@@ -32,8 +32,8 @@ deployApp(
 )
 }
 \arguments{
-\item{appDir}{Directory containing application. Defaults to current working
-directory.}
+\item{appDir}{A directory containing an application (e.g. a Shiny app
+or plumber API). Defaults to the current directory.}
 
 \item{appFiles}{A character vector given relative paths to the files and
 directories to bundle and deploy. The default, \code{NULL}, will include all
diff --git a/man/showMetrics.Rd b/man/showMetrics.Rd
index a480f924..ad6a912f 100644
--- a/man/showMetrics.Rd
+++ b/man/showMetrics.Rd
@@ -25,8 +25,8 @@ for available series.}
 \href{https://docs.posit.co/shinyapps.io/metrics.html#ApplicationMetrics}{shinyapps.io documentation}
 for available metrics.}
 
-\item{appDir}{Directory containing application. Defaults to current working
-directory.}
+\item{appDir}{A directory containing an application (e.g. a Shiny app
+or plumber API). Defaults to the current directory.}
 
 \item{appName}{Name of application (names must be unique within an account).
 If not supplied on the first deploy, it will be generated from the base
diff --git a/man/writeManifest.Rd b/man/writeManifest.Rd
index 1b4fa01c..95fc8e0f 100644
--- a/man/writeManifest.Rd
+++ b/man/writeManifest.Rd
@@ -17,8 +17,8 @@ writeManifest(
 )
 }
 \arguments{
-\item{appDir}{Directory containing application. Defaults to current working
-directory.}
+\item{appDir}{A directory containing an application (e.g. a Shiny app
+or plumber API). Defaults to the current directory.}
 
 \item{appFiles}{A character vector given relative paths to the files and
 directories to bundle and deploy. The default, \code{NULL}, will include all
diff --git a/tests/testthat/_snaps/deployApp.md b/tests/testthat/_snaps/deployApp.md
index 4715b789..d0b1a263 100644
--- a/tests/testthat/_snaps/deployApp.md
+++ b/tests/testthat/_snaps/deployApp.md
@@ -1,3 +1,27 @@
+# appDir must be an existing directory
+
+    Code
+      deployApp(1)
+    Condition
+      Error in `deployApp()`:
+      ! `appDir` must be a single string, not the number 1.
+    Code
+      deployApp("doesntexist")
+    Condition
+      Error in `deployApp()`:
+      ! `appDir`, "doesntexist", does not exist.
+
+# single document appDir is deprecated
+
+    Code
+      deployApp("foo.Rmd")
+    Condition
+      Warning:
+      The `appDir` argument of `deployApp()` takes a directory, not a document, as of rsconnect 0.9.0.
+      i Please use `deployDoc()` instead.
+      Error in `deployDoc()`:
+      ! `doc`, "foo.Rmd", does not exist.
+
 # appPrimaryDoc must exist, if supplied
 
     Code
diff --git a/tests/testthat/_snaps/deployDoc.md b/tests/testthat/_snaps/deployDoc.md
new file mode 100644
index 00000000..6f76bb70
--- /dev/null
+++ b/tests/testthat/_snaps/deployDoc.md
@@ -0,0 +1,8 @@
+# deployDoc correctly reports bad path
+
+    Code
+      deployDoc("doesntexist.Rmd")
+    Condition
+      Error in `deployDoc()`:
+      ! `doc`, "doesntexist.Rmd", does not exist.
+
diff --git a/tests/testthat/test-deployApp.R b/tests/testthat/test-deployApp.R
index d4ee668c..b3d234bf 100644
--- a/tests/testthat/test-deployApp.R
+++ b/tests/testthat/test-deployApp.R
@@ -1,3 +1,16 @@
+test_that("appDir must be an existing directory", {
+  expect_snapshot(error = TRUE, {
+    deployApp(1)
+    deployApp("doesntexist")
+  })
+})
+
+test_that("single document appDir is deprecated", {
+  expect_snapshot(error = TRUE, {
+    deployApp("foo.Rmd")
+  })
+})
+
 test_that("appPrimaryDoc must exist, if supplied", {
   dir <- local_temp_app()
 
diff --git a/tests/testthat/test-deployDoc.R b/tests/testthat/test-deployDoc.R
new file mode 100644
index 00000000..6d071152
--- /dev/null
+++ b/tests/testthat/test-deployDoc.R
@@ -0,0 +1,43 @@
+test_that("deployDoc correctly reports bad path", {
+  expect_snapshot(deployDoc("doesntexist.Rmd"), error = TRUE)
+})
+
+# standardizeSingleDocDeployment ------------------------------------------
+
+test_that("turns appDir into appDir + appPrimarySourceDoc", {
+  dir <- local_temp_app(list("foo.R" = ""))
+
+  doc <- standardizeSingleDocDeployment(file.path(dir, "foo.R"))
+  expect_equal(doc$appDir, normalizePath(dir))
+  expect_equal(doc$appPrimaryDoc, "foo.R")
+})
+
+test_that("shiny rmd deploys whole directory", {
+  dir <- local_temp_app(list("foo.Rmd" = c(
+    "---",
+    "runtime: shiny",
+    "---"
+  )))
+  doc <- standardizeSingleDocDeployment(file.path(dir, "foo.Rmd"))
+  expect_equal(doc$appFiles, NULL)
+})
+
+test_that("regular rmd deploys file and dependencies", {
+  dir <- local_temp_app(list(
+    "foo.Rmd" = c(
+      "---",
+      "resource_files: [foo.csv]",
+      "---"
+    ),
+    "foo.csv" = ""
+  ))
+
+  doc <- standardizeSingleDocDeployment(file.path(dir, "foo.Rmd"), quiet = TRUE)
+  expect_equal(doc$appFiles, c("foo.Rmd", "foo.csv"))
+})
+
+test_that("other types deploy that one file", {
+  dir <- local_temp_app(list("foo.R" = ""))
+  doc <- standardizeSingleDocDeployment(file.path(dir, "foo.R"))
+  expect_equal(doc$appFiles, "foo.R")
+})